Density and XERF — Both “Use Two Things,” but They Combine Along Different Axes
“Which is better, Density or XERF?” — first, the disclosure. No study comparing the two devices directly in humans has been identified. A 2026 systematic review (15 papers · 1,230 people) also stated explicitly that “no head-to-head comparison between devices was identified.” Both are introduced as “using two things,” but they combine along different axes — Density combines polarities, XERF combines frequencies.
The short answer
No study comparing Density and XERF directly in humans has been identified. A 2026 systematic review (15 papers · 1,230 people) stated explicitly that “no head-to-head comparison between devices was identified,” and did not perform a meta-analysis because of heterogeneity. So there is no data behind a sentence such as “this one penetrates better.” Both devices are introduced as “using two things,” but they combine along different axes — Density uses two polarities (monopolar then bipolar in sequence), while XERF uses two frequencies (6.78 MHz + 2 MHz) monopolar. It sounds like the same claim, but what changes differs — polarity changes whether current passes through the body; frequency changes where within tissue the heat concentrates. As for the thickness of the evidence, both are thin and neither has a control group — XERF has one human study (20 people · single arm · 12 weeks), Density has 16 people (3D measurement 0.82 ± 0.36 mm).
The comparison on one page
| Item | Density | XERF |
|---|---|---|
| Manufacturer | Jeisys Medical, Republic of Korea | Lutronic, Republic of Korea |
| Delivery mode | Monopolar then bipolar, in sequence | Monopolar |
| Frequency | 6.78 MHz | 6.78 MHz + 2 MHz |
| Axis combined | Polarity | Frequency |
| Maximum output | 400 W | We could not find this in the manufacturer’s published specifications |
| Epidermal protection | Gas cooling, five levels | Cryogen spray |
| Output correction | RIC — automatic adjustment to impedance by area | Impedance feedback |
| Temperature management | Real-time skin temperature display during treatment | Surface kept below 43 °C in porcine preclinical work |
| Tips · handpieces | ALPHA · Eye · Face · Body, four types | XERF i05 · i10, EFFECTOR E40 · E60, four types |
| US FDA | We could not verify | 510(k) K251327 (2025-08-11) |
| Human data | 16 people, 3D measurement 0.82 ± 0.36 mm | 20 people, single arm · 12 weeks (Medical Lasers 2025;14(1):23–30, DOI 10.25289/ML.24.035) |
| Control group | None | None |
Combining polarities versus combining frequencies
What each device was aiming at divides here.
Density — it switches polarity in sequence. Monopolar has a single electrode, so current passes through the body and exits at a return pad. Bipolar confines current to the narrow span between two electrodes. But what sets the depth is not polarity itself but the shape and arrangement of the electrodes — for monopolar the size of the electrode governs heating depth; for bipolar it is the spacing between electrodes. In data combining finite element analysis with tissue measurement, a widely spaced bipolar applicator came out 1.9–5.7 times deeper than monopolar electrodes (J Biomed Sci Eng 2024 — all authors were employees of the device manufacturer). The detail is in monopolar and bipolar — what differs.
XERF — it uses two frequencies. In 2025 data combining computer simulation with porcine histology, 2 MHz heated the fat layer broadly and deeply while 6.78 MHz heated focally along the fibrous septa. That is, changing the frequency changes where the heat concentrates.
One thing to be clear about. The two paragraphs above are mechanism and preclinical data, not data showing that “the result on a human face is therefore better.” No study confirming that link exists for either device.
Putting the thickness of the evidence side by side
| What | Density | XERF |
|---|---|---|
| Number of human studies | One identified (16 people) | One identified (20 people) |
| Design | No control group | Single arm · no control · single centre, one session, 12 weeks |
| What was measured | 3D measurement 0.82 ± 0.36 mm | Blinded assessors correctly identified the after photograph 80% of the time, GAIS 2.75/4, patient satisfaction 7.84/10 |
| Pain | We could not verify | Without anaesthesia, VAS 4 in 9 people · 5 in 11 people |
| Adverse events | We could not verify | Reported as none |
| Conflict of interest | We could not verify | Declared no conflict of interest and no funding |
| Journal indexing | We could not verify | Indexed in KCI and KoreaMed — not in PubMed/MEDLINE or SCIE |
| Remaining data | — | Five preclinical papers, all with manufacturer-affiliated authors or company sponsorship |
What matters most is that neither device has a control group. Without a control you cannot tell how much of the observed change was due to the treatment. Across radiofrequency lifting generally, of the 15 papers and 1,230 people gathered by the 2026 systematic review, only one was a randomised controlled trial.
What actually decides the choice
With no direct comparison, what we put in front of people in consultation is not the device name but the conditions.
- Which layer is being addressed. Both devices treat the dermis and the structures beneath it with heat. Hollowed volume, pigment and severe laxity are not solved by either.
- Skin thickness and fat volume. At the same output, epidermal protection design weighs more heavily in thin skin. The relevant criteria are in choosing a lifting treatment by skin thickness and fat.
- Pain tolerance. In the XERF study, VAS without anaesthesia was 4–5. That figure is based on 20 people and individual variation is large.
- When to judge. The assessment point for radiofrequency is not the same day but two to three months later. In an assessor-blinded study of 20 Korean women, radiofrequency was not significant on clinician assessment at 4 weeks but was at 12 weeks, with a peak at 4–6 months. Set out in when improvement shows, and when to judge it.
Frequently asked questions
Which one hurts more?
There is no data comparing the two devices under the same conditions. On the XERF side there is a figure — without anaesthesia, VAS 4 in 9 people and 5 in 11 people (out of 20). We could not verify a pain figure for Density.
If Density is 400 W, is it stronger?
Output in watts is the maximum the device can produce, not the energy delivered to the skin. Actual heating is set together by frequency, electrode arrangement, exposure time and tissue impedance. The two devices cannot be compared on maximum output alone.
Is XERF FDA approved?
It has 510(k) K251327 (2025-08-11). A 510(k) is a notification route asserting “substantial equivalence to an already cleared device,” and it is different from PMA approval, which requires clinical trials demonstrating effectiveness. This distinction is frequently blurred in citation.
Can I just compare shot counts?
A “shot” is not a dose the practitioner sets but a pulse-count specification sealed into the single-use tip in advance. XERF has a maximum shot count per tip (i05 400 · i10 300 · E40 600 · E60 600). What the shot count really is, is set out in how many shots do you need.
Isn’t using both monopolar and bipolar better?
No study has made that comparison. “Using two things” is a design characteristic, and whether it leads to a better result on a human face has not been verified. And what sets the depth is not polarity itself but the shape and arrangement of the electrodes.
Are both approved in Korea?
Density is an MFDS-approved medical device. XERF is also an MFDS-approved medical device, but no published approval number has been identified, and its approval category is general electrosurgical unit. How to look one up by approval number is in checking an approval number yourself.
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
- Medical Lasers 2025;14(1):23–30, DOI 10.25289/ML.24.035 — XERF human study, 20 women aged 28–63, Fitzpatrick III–IV, single arm · no control · single centre, one session, 12-week follow-up, blinded assessors correctly identified the after photograph 80% of the time, GAIS 2.75/4, satisfaction 7.84/10, VAS 4 in 9 people · 5 in 11 people, no adverse events, no conflict of interest or funding declared. Indexed in KCI and KoreaMed.
- US FDA 510(k) K251327 (2025-08-11) — XERF.
- Density human data — 16 people, 3D measurement 0.82 ± 0.36 mm, no control group.
- Computer simulation + porcine histology (2025) — 2 MHz heated the fat layer broadly and deeply; 6.78 MHz heated focally along the fibrous septa. Surface kept below 43 °C in XERF porcine preclinical work.
- J Biomed Sci Eng 2024 — finite element analysis plus tissue measurement; all authors were employees of the device manufacturer.
- 2026 systematic review — 15 papers · 1,230 people, one randomised controlled trial, no meta-analysis performed because of heterogeneity, “no head-to-head comparison between devices was identified.”
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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