The four EFFECTOR tips — what changes when the tip changes
“Does a bigger tip go deeper?”, “Is a smaller tip stronger?” — both come up often in consultations. The point of this piece is that the answers to those two questions run in opposite directions. With a small tip the current crowds into a narrow spot and heats it harder, while the depth, if anything, is greater with the larger tip — that is the direction in which the physics and measurements from other fields point. But we have to stop there — we did not find a study that actually measured depth by tip size in human skin, and the only study in humans that compared tip sizes failed to show a statistical difference between the two tips. And yet the concluding sentence of that paper is written as though there were one.
The conclusion, first
A small tip is stronger and a large tip is deeper — the two sentences are not a contradiction; they are about different things. For the same current, the smaller the electrode area the higher the current density, and the temperature rise in tissue is proportional to the square of the current density. So a narrow tip heats a narrow spot harder. Depth, conversely, is greater with a larger electrode — that is the direction in which the physical accounts and measurements from other clinical fields point. In cardiac procedures an 8 mm electrode made a deeper lesion than a 4 mm one, and in pain medicine going from a 22G to a 16G needle widened the lesion by 58–65%. Three things have to be made clear here, though. First, this relationship is not unconditional — there is an experiment in which, with the output held fixed, the larger electrode was not deeper. Second, we did not find a study measuring depth by tip area in human skin. Third, the only study in humans comparing tip sizes found the difference between the two tips statistically non-significant (p=0.845) — and yet the concluding sentence of that paper is written as though there were a difference. So the criterion for choosing a tip in practice is not “how many millimetres does it reach” but “does this tip sit evenly on this part of the face”.
The certain part first — narrower means stronger
This part is not a story about aesthetic treatment but the basic principle of electrosurgery, and it is established at textbook level.
Radiofrequency is not light but current. When the same amount of current flows through a smaller area, the current density goes up. And the temperature rise in tissue is proportional to the square of the current density — double the density and the heating is four times greater.
| Electrode | Area | Result |
|---|---|---|
| Surgical cutting electrode | Shaped as a needle · hook, brought to a point | Current density raised to a maximum, so it cuts |
| Coagulating electrode | Broad and flat | Current density lowered, heating slowly, so it coagulates |
| Return pad on the body | Very broad | Current density falls extremely low, so that site does not get hot |
This explains why the pad stuck to your back or body during an XERF treatment is so large. Exactly the same current flows through that pad as through the tip touching your face. The reason it is nonetheless not hot is that the area is tens of times wider, so the current density drops to the floor. It is the other face of precisely the same principle by which a smaller tip is stronger.
So to the question “is a smaller tip stronger” we can answer yes, all else being equal. But real devices adjust output to tip area, so it does not follow that “small tip = a stronger treatment”.
Which one goes deeper
This is where the received view is often overturned. A small tip heats harder, so you would expect it to go deeper too — but the literature points the other way.
| Source | Comparison | Result |
|---|---|---|
| Cardiac catheter ablation (1998) | 8 mm versus 4 mm electrode | The 8 mm made a deeper lesion under every condition — the title of the paper is itself “why a large tip electrode makes a deeper lesion” |
| Pain medicine radiofrequency (2014) | 22G versus 16G needle | At 80°C for 2 minutes, lesion width up 58–65% |
| Physical account | Electrode radius | The statement that penetration depth is proportional to the electrode radius — several aesthetic RF papers build on this premise |
| Counter-example (2009) | The same 8 mm versus 4 mm | In vitro under temperature control, the 8 mm was not deeper |
The last row matters. “Larger electrode = deeper” is a conditional proposition. Two mechanisms are offered for why a large electrode goes deeper — the wider contact area spreading the current more broadly and more deeply, and the electrode cooling better, so heat builds up underneath while the surface does not burn. Where the output is held fixed and the second mechanism cannot operate, the relationship does not hold.
This is the point at which we stop. Those measurements were obtained with needle · catheter electrodes in cardiac muscle and around nerves, which is not the same as laying a flat tip on facial skin. The widely quoted formula “penetration depth = about one third of the electrode radius” is one for which we did not find a primary source setting out the derivation, and the “depth” it speaks of is not the depth a clinical effect reaches but the distance over which the heating falls by a fixed ratio. So we do not put a millimetre figure for each tip in this piece. We could calculate one and write it down, but that would be arithmetic, not evidence.
In human skin it has not been measured yet
Here is a fact you may find surprising. We did not find a single study that actually measured and compared depth or temperature in human skin by tip area.
- Even for the Thermage family, the longest-selling monopolar devices, no study comparing between tip areas (0.25 · 1.0 · 1.5 · 3.0 cm²) is confirmed.
- Not even the manufacturer's technical manual describes the relationship between tip size and heating depth.
- The XERF simulation study also used only one type of tip, so the effect of tip size is not addressed — the variable that study handled was frequency.
That is, an account of “this tip reaches this far” is an estimate drawn from a physical model, not a measurement. Not that the estimate is wrong, but that you should hear it as distinct from a confirmed fact.
The one human study comparing tip size — and its concluding sentence
There is exactly one. It was done with another company's monopolar device.
| Item | Detail |
|---|---|
| Design | A 3 cm² tip on one side of the face and a 4 cm² tip on the other, randomly assigned |
| Subjects | 31 people (28 women · 3 men), aged 29–75, one session, three months of follow-up |
| Dose | 300 shots on both sides, 16.4 versus 16.6 J/cm² per area — effectively the same |
| The authors' conclusion | “The smaller tip is better for upper facial wrinkles, the larger tip for lower facial laxity” |
| The actual statistics | The difference between the two tips was not significant — p=0.845 |
This part has to be read carefully. The p<0.001 that appears in the paper is not “the small tip side did better than the large tip side” but “the area treated with the small tip improved compared with before treatment”. A before-and-after comparison and a comparison of two tips are different questions. The value putting the two tips against each other is p=0.845, a level at which no difference can be claimed. And yet the concluding sentence of the paper is written as though there were one.
So the statement “research has proved a small tip is more effective around the eyes” cannot be made from this paper. The accurate statement is — “a tendency of that kind was observed but could not be distinguished statistically”. On top of that, the study measured neither temperature nor depth; it scored wrinkles only.
The four XERF tips
| Handpiece | Stated area | Maximum shots | Mainly used on |
|---|---|---|---|
| XERF i05 | 5 × 10 mm | 400 shots | Narrow, thin areas |
| XERF i10 | 10 × 10 mm | 300 shots | Small, curved areas |
| EFFECTOR E40 | 20 × 20 mm | 600 shots | All areas |
| EFFECTOR E60 | 20 × 30 mm | 600 shots | Broad, thick areas |
Here we set down, as it stands, one inconsistency we found.
The electrode pattern dimensions in the summary filed with the US FDA differ from the table above. The summary gives the 60 tip as 27.6 × 17.6 mm, the 40 tip as 17.6 × 17.6 mm, the 10 tip as 9 × 9 mm and the 05 tip as 9 × 4.5 mm. The study in humans likewise records the E60 as 27.6 × 17.6 mm (about 4.86 cm²). That is about a 20% difference from the marketing figure (20 × 30 mm = 6.0 cm²). It looks as though the outer dimension and the dimension of the pattern the current actually flows through are different, but which of the two is the real conducting area we were not able to confirm. So please read the figures in the table above as “on the manufacturer's stated basis” only.
What is really worth noticing in the table is not the area but that the maximum shot count differs from tip to tip. That is the subject of the next piece.
Change the tip and ‘the same 300 shots’ is not the same
Shot count is the customary unit for stating how much treatment was given. But with a different tip the same number is an entirely different amount.
| Tip | Nominal area of 300 shots | Note |
|---|---|---|
| 3 cm² | 900 cm² | Reference |
| 4 cm² | 1,200 cm² | 33% wider |
| 0.25 cm² (eye tip) | 75 cm² | About 1/12 |
The figures in the table are nominal values we calculated as tip area × shot count, with no allowance for overlapping passes. Even so the direction is clear — the number “how many shots” is not a complete statement unless the tip is named alongside it. That story continues in how many shots should I have.
“Does a smaller tip hurt more?”
There is no material to answer with. We did not find a study that compared pain with tip area as the variable. The split-face study above did measure pain, but did not report it broken down by tip.
For reference, the pain reported under single-tip conditions varies greatly from study to study — in the XERF human study, without anaesthesia, 4–5 out of 10; in another study 0.61; under the early Thermage protocol 6. That spread is more likely to come from differences in output setting and protocol than from tip size.
The rule we use in practice is simple. If it feels “hot” during the treatment, please do not endure it — say so straight away. That signal is what we set the output by. Pain is not a discomfort to be borne but a safety signal — there is more on this in aftercare following RF treatment.
Things that matter more than the tip
We have talked about tips at length, but among the factors setting how much heat goes where, tip size is not the largest.
| Factor | Effect | Level of evidence |
|---|---|---|
| Temperature (output) | Going from 60°C to 90°C widens the lesion by 108–152% | Quantitatively established — the largest |
| Delivery time | Going from 1 minute to 3 minutes adds 23–32% | Quantitatively established — smaller than temperature |
| Surface cooling | Cooling the surface to create a state in which it is hotter underneath is the core design of this treatment | The role is established, the values differ by device |
| Tissue impedance | As tissue heats, resistance falls by about 2% per degree — part of why people differ | A quantitative relationship exists |
| Frequency | Changes not the depth but where between tissues the current is drawn | Modelling + animal |
| Tip area | Changes the current density and the extent of contact | No measurement in humans |
| Pressure applied · state of contact | Likely to have an effect, but | No quantitative data found |
The relationship between temperature and time changes the character of this treatment. Collagen changes according to how long it stayed at a temperature, not only what temperature it reached — in measurements, the denaturation index of skin collagen fell to half in 16 seconds at 70°C, but at 55°C only 25% changed in two hours, and at 50°C only 2%. That story is set out in detail in monopolar and bipolar.
So what do we actually go by when choosing
In the end the real criterion for choosing a tip is not a depth figure but contact.
- Put a broad tip on a narrow place and the contact lifts. Where it lifts, the current does not flow evenly.
- Sweep a broad surface with a small tip alone and the delivery is not uniform, and it takes far longer to cover the same area.
- Sharply curved regions, regions passing thinly over bone, and structurally different regions such as around the eyes cannot be handled with the same tip.
The reason there are several tips is less “to select a depth” than “because the face is not flat”. That is so within the range we can speak to from the evidence.
In summary
| Confirmed | Could not confirm |
|---|---|
| The smaller the area the higher the current density, with temperature rise proportional to its square | Measured depth · temperature by tip area in human skin |
| The return pad is broad on the same principle | The primary source of the “depth = one third of the electrode radius” formula |
| Measurements in other fields support “the larger electrode is deeper” | Whether that relationship holds for a flat tip on the face |
| The existence of the one human tip comparison study | A statistical difference between the two tips in that study — there was none |
| The manufacturer's stated specifications for the four XERF tips | The actual conducting area — the figures differ between sources |
| The effects of temperature · time · cooling | The relationship between tip size and pain |
Frequently asked questions
Does a bigger tip go deeper?
The physics and measurements from other clinical fields support that direction. But there is no study that actually measured depth by tip size in human skin. And in an experiment where the output was held fixed the larger electrode was not deeper, so the relationship is not unconditional. That is why we do not write “this tip reaches so many mm”.
Is a smaller tip a stronger treatment?
For the same current, it crowds into a smaller area, so that spot is heated harder. The temperature rise is proportional to the square of the current density. But real devices adjust the output to the tip area, so using a small tip does not make the whole treatment stronger.
Why is the pad stuck to my body so large?
Because exactly the same current returns through that pad as passes through the tip. The area has to be tens of times wider for the current density to fall low enough that the site does not get hot. It is the other face of the same principle by which a smaller tip is stronger. That is also why it matters for safety that the pad is properly attached.
I have heard a small tip is better around the eyes.
A paper says so, but in that paper the difference between the two tips was not statistically significant (p=0.845). The p<0.001 inside it means “better than before treatment”, not “better than the other tip”. The real reason a small tip is used around the eyes is closer to the fact that a large tip does not sit evenly there.
Does a different tip size mean a different level of pain?
There is no material to answer with. We did not find a study comparing pain with tip area as the variable. Reported pain ranges widely between studies, from 0.6 to 6 out of 10, and that spread appears to come from output settings and protocol rather than the tip.
The XERF tip specifications seem to differ between sources.
They do. The manufacturer gives the E60 as 20 × 30 mm, while the summary filed with the US FDA and the published paper give 27.6 × 17.6 mm. It looks like the difference between the outer dimension and the dimension of the conducting pattern, but which of the two is the real conducting area we were not able to confirm. So the figures in this piece are on the manufacturer's stated basis.
Can I ask for a particular tip, then?
It is settled by the region, so it is not really something to choose in advance. Put a broad tip on a narrow curved place and the contact lifts; sweep a broad surface with a small tip alone and it is not uniform. But “which tip are you using where today” is a good question to ask.
Could the whole face not be done with one large tip?
Places it physically cannot reach would appear. The face is not flat, so sharply curved places such as around the eyes · beside the nostrils · under the jawline make a broad tip lift. Where it lifts, the current does not flow evenly, so the delivery ends up uneven.
So is the tip story not really important?
It is important, but it is not the most important thing. Among the factors setting how much heat goes where, the one confirmed as largest in quantitative terms is temperature (output), then time, with cooling protecting the surface. Tip size comes after those, and it is the item with no measurement in humans.
Who wrote this
Written and reviewed by Lee Chi-Hak, MD, medical director of Miso Clinic in Daegu, South Korea. Every study cited above is given together with its design, its size and the limitations the authors themselves recorded, and where we could not find data, we have said that we could not find any.
| Medical director | Lee Chi-Hak, MD |
|---|---|
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References
- Current density and electrode area — an established principle — Li AA, Zhou MJ, Hwang JH. Understanding the Principles of Electrosurgery for Endoscopic Surgery and Third Space Endoscopy. Gastrointestinal Endoscopy Clinics of North America 2023;33(1):29–40, DOI 10.1016/j.giec.2022.07.001 (full text confirmed). “temperature in tissue rises as a square of the current density”, and on the return pad “Because the surface area of the pad is orders of magnitude larger than the active device, the current density is extremely low at the pad site.” / El-Sayed MM, Saridogan E. Principles and safe use of electrosurgery in minimally invasive surgery. Gynecology and Pelvic Medicine 2021;4:6, DOI 10.21037/gpm-2020-pfd-10 (full text confirmed) — cutting electrodes brought to a point, coagulating electrodes made broad.
- “The larger electrode is deeper” — direct measurement in other fields — Otomo K, Yamanashi WS, Tondo C et al. Why a large tip electrode makes a deeper radiofrequency lesion: effects of increase in electrode cooling and electrode-tissue interface area. Journal of Cardiovascular Electrophysiology 1998;9(1):47–54, PMID 9475577 (abstract confirmed). Canine thigh muscle + perfusion model, the 8 mm electrode making a significantly deeper lesion than the 4 mm under every condition, the mechanism being increased convective cooling + increased contact area. / Cosman ER Jr, Dolensky JR, Hoffman RA. Factors that affect radiofrequency heat lesion size. Pain Medicine 2014;15(12):2020–2036, PMID 25312825 (full text confirmed). Going from 22G to 16G widens the lesion by 58–65% (3–4 mm) at 80°C for 2 minutes, temperature 60 to 90°C gives a 108–152% increase, and time 1 to 3 minutes a 23–32% increase.
- The counter-example — Linhart M, Mollnau H, Bitzen A et al. In vitro comparison of platinum–iridium and gold tip electrodes: lesion depth in 4 mm, 8 mm, and irrigated-tip radiofrequency ablation catheters. Europace 2009;11(5):565–570, PMID 19251707 (abstract · figures confirmed). In liver tissue, 4 mm 4.67 ± 1.7 mm versus 8 mm 3.98 ± 1.0 mm, so the larger electrode was not deeper. In vitro under temperature control, with no convective cooling from blood flow. Because of this counter-example, “larger electrode = deeper” cannot be used unconditionally.
- The source problem with “depth = about one third of the electrode radius” — the
d = 0.28 r₀of Kreindel M, Mulholland S. The Basic Science of Radiofrequency-Based Devices, IntechOpen 2021, DOI 10.5772/intechopen.96652 (full text confirmed). It is offered with no derivation, only as “It is easy to calculate”, and we were not able to trace the original source back. The author belongs to the radiofrequency device industry. The “penetration depth” here is the characteristic distance over which the heating falls to 1/e, not the depth a clinical effect reaches. A clinical paper building on the same figure — Journal of Clinical and Aesthetic Dermatology 2024;17(2):20–22, “RF energy penetration depth is about one third of electrode radius”. - The only human study comparing tip area — Yang YS, Kim DH, Ha JH et al. A Split-face Study on Rejuvenation Efficacy According to Monopolar Radiofrequency Tip Size. Journal of Clinical and Aesthetic Dermatology 2024;17(2):20–22, PMID 38444428 (full text confirmed). Volnewmer (Classys), 3 cm² versus 4 cm² split-face randomised, 31 people (28 women · 3 men), aged 29–75, 300 shots each, 16.4 versus 16.6 J/cm², surface water cooling at 12–14°C, three months of follow-up. The authors conclude “small tip for the upper face, large tip for the lower face”, but the comparison value between the two tips given in the text is p=0.845, which is not significant. The significant p<0.001 is the before-and-after comparison. Temperature · depth were not measured; only wrinkle scores were assessed. Adverse events — one mild erythematous burn on the forehead in the 4 cm² area (resolved within a week). Limitations stated by the authors — small sample, wide age range, short three-month follow-up. Because the text carries a unit error, with
16-19kJ/cm²and16.4 J/cm²both written, we have not cited the total energy figures from this paper. - Thermage tip specifications — Chilukuri S, Lupton J. “Deep Heating” Noninvasive Skin Tightening Devices: Review of Effectiveness and Patient Satisfaction. Journal of Drugs in Dermatology 2017;16(12):1262–1266 (full text confirmed). Tips of 0.25 · 1.0 · 1.5 · 3.0 cm², the dermis heated to 65–75°C with the epidermis held at 40°C, and pain 6 out of 10 without pain management. We did not find a study comparing between tip areas, and the manufacturer's technical manual does not describe the relationship between tip size and heating depth either.
- XERF tip specifications and the discrepancy — the manufacturer's published specifications are XERF i05 5 × 10 mm (400 shots) · i10 10 × 10 mm (300 shots) · EFFECTOR E40 20 × 20 mm (600 shots) · E60 20 × 30 mm (600 shots). The electrode pattern dimensions in the US FDA 510(k) K251327 summary are 60 Tip 27.6 × 17.6 mm · 40 Tip 17.6 × 17.6 mm · 10 Tip 9 × 9 mm · 05 Tip 9 × 4.5 mm, which differ, and the study in humans (Medical Lasers 2025;14(1):23–30) also records the E60 as 27.6 × 17.6 mm (4.86 cm²). Which of the two is the real conducting area we were not able to confirm. The XERF simulation study (Lasers in Medical Science 2025;40:501) used only one type of tip, 20 × 30 mm, and its variable was frequency.
- Cooling and impedance — measured surface temperatures differ by device — the Thermage family dermis 65–75°C / epidermis 40°C, Volnewmer surface 12–14°C, XERF preclinical surface below 42–45°C. Impedance falls by about 2% per °C on heating and rises sharply with dehydration around 100°C (Kreindel 2021). The power relation
E(J) = I² × z × t— Shin JM, Kim JE. Radiofrequency in Clinical Dermatology. Medical Lasers 2013;2(2):49–57, DOI 10.25289/ML.2013.2.2.49 (full text confirmed). - Temperature × time — Cellular and Molecular Bioengineering 2021, DOI 10.1007/s12195-020-00653-w. For the crimp contrast of skin collagen to fall by half, 16 seconds at 70°C · 90 seconds at 65°C · 110 seconds at 60°C, with 25% in two hours at 55°C and 2% in two hours at 50°C. The details are in monopolar and bipolar.
- Reference values for pain — the XERF human study (Medical Lasers 2025;14(1)) VAS 4–5 without anaesthesia / JCAD 2024 mean 0.61 · 54.8% pain-free / JDD 2017 early Thermage protocol 6. There is no material examining the relationship between tip area and pain. The quantitative effect of applied pressure · uniformity of contact we were not able to confirm either.
- What we were not able to confirm — (1) measured depth · temperature by tip area in human skin (2) the primary derivation source for the “one third of the electrode radius” formula (3) a study comparing between Thermage tip areas (4) tip area and pain (5) the quantitative effect of pressure · state of contact (6) the real conducting area and individual output (W) of each XERF tip (7) verification of whether a spherical electrode formula can be applied to a flat square tip.
- Continuing pieces — how many shots should I have, how far the evidence for XERF has come, monopolar and bipolar, the comparison of three RF devices.
Everything in this column is general information and does not replace medical diagnosis or treatment. Effects and side effects vary with individual skin condition, age and underlying illness, and the same result is not guaranteed for everyone. Any decision to proceed should be made in an in-person consultation with a physician.
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