XERF vs Thermage FLX in Korea: How the Two RF Devices Differ

Updated October 2026.

Medically reviewed by Dr. Kwangsuk Suh, board-certified dermatologist.

If you have been reading about skin tightening in Korea, you have probably met both names in the same week. Thermage has been the reference point for radiofrequency tightening for many years. XERF is the newer Korean device that clinics in Seoul now offer alongside it. The question most patients bring to the consultation is a fair one: are these two different treatments, or two versions of the same idea?

The honest answer is somewhere in between. XERF and Thermage FLX share a principle, and the regulatory record makes that explicit. They differ in how the energy is delivered and controlled, and in how much published evidence sits behind each one. This guide sets out what is the same, what is different, what the evidence does and does not show, and how a doctor decides between them. It is written for international patients, and our coordinators can help with appointment questions.

The Short Answer

Both XERF and Thermage FLX are monopolar radiofrequency devices. Both heat the deeper skin through a cooled surface, which tightens existing collagen and prompts new collagen to form over the following months. Thermage FLX works at a single frequency, 6.78 MHz. XERF combines that same frequency with a second, lower one, 2 MHz, and lets the doctor choose between three depth settings. Thermage FLX has the longer track record and a larger body of published experience; XERF is newer, and its published studies so far are small and short. Neither is “better” in a general sense. The choice depends on your skin thickness, the area, whether the eyelids are involved, and how you have responded to energy treatments before.

What XERF and Thermage FLX Have in Common

The same family of device. Both are monopolar radiofrequency systems: energy passes from a disposable treatment tip on the skin to a return pad placed elsewhere on the body, and the tissue in between is heated. The surface is cooled during each pulse so that the heat builds underneath rather than at the top of the skin.

The same regulatory starting point. In the United States, devices are often cleared by showing they are substantially equivalent to one already on the market. XERF’s 510(k) summary, published by the FDA, names Thermage FLX as its predicate device. The same filing describes a laboratory comparison in which temperature sensors were placed 3 mm into ex vivo skin, and reports that XERF’s heating and cooling curves were equivalent to those of Thermage FLX under the tested conditions. No clinical tests were included in that submission.

The same biological goal. For both devices the intended effect is the same: controlled heating that contracts collagen and triggers remodelling over time. Neither repositions deep structures the way surgery does, and neither is a substitute for a facelift when laxity is heavy.

Where They Differ

Who makes them

Thermage FLX is made by Solta Medical, the aesthetic business of Bausch Health, and is the fourth generation of the Thermage platform. XERF is made by Lutronic, now part of Cynosure Lutronic, in Goyang, Korea. Lutronic states that XERF received Korean MFDS approval in January 2024, and it was later cleared in the United States in 2025.

Frequency

Thermage FLX delivers radiofrequency at 6.78 MHz. XERF delivers 6.78 MHz and 2 MHz. Lutronic’s rationale is that the lower frequency acts more deeply in the skin than the higher one. A computer model and animal study from researchers including the manufacturer’s team found that 2 MHz produced a wider and deeper heating pattern than 6.78 MHz at the same total energy. That depth difference has not yet been measured directly in human facial skin, a limitation the clinical authors acknowledge.

Depth settings and how energy is adjusted

XERF offers three depth settings (shallow, middle and deep) and ten energy levels. In published protocols the shallow setting uses 6.78 MHz alone, and the deep setting delivers 6.78 MHz followed by 2 MHz within a single pulse. The device reads tissue impedance and monitors the surface temperature of the tip with each pulse, and in published studies RF output stops automatically if the tip surface exceeds 43°C.

Thermage FLX does not use depth modes in the same way. Depth and coverage are shaped mainly by the choice of tip and the energy level. Its AccuREP technology reads skin impedance and adjusts RF output with each pulse, according to Solta.

Tips

Thermage FLX tips include a 4.0 cm² and a 3.0 cm² face tip, a 0.25 cm² eye tip for shallow heating around the eyes, and a 16.0 cm² body tip. Solta states that the 4.0 tip covers a larger area per pulse than the 3.0 tip, which shortens treatment time.

XERF uses disposable tips called effectors. Its FDA filing lists four effector sizes, from 9 x 4.5 mm to 27.6 x 17.6 mm, with the smaller ones used around the eyes in published protocols.

Cooling and comfort features

Thermage FLX pairs each pulse with a cooling burst and built-in vibration intended to ease the sensation. XERF uses integrated cryogen cooling with an adjustable level, and spreads its energy across a train of shorter sub-pulses rather than a single burst.

XERF vs Thermage FLX at a Glance

	XERF	Thermage FLX
Energy	Monopolar radiofrequency	Monopolar radiofrequency
Frequency	6.78 MHz and 2 MHz	6.78 MHz
Manufacturer	Lutronic (Cynosure Lutronic), Korea	Solta Medical (Bausch Health)
Depth control	Three depth settings, ten energy levels	Tip choice and energy level
Energy adjustment	Impedance feedback and tip surface temperature monitoring	AccuREP impedance reading with each pulse
Comfort features	Integrated cryogen cooling, sub-pulsed delivery	Cooling bursts with vibration
Eye area	Small effectors used in published periorbital protocols	Dedicated 0.25 cm² eye tip, with eye shields
Published clinical evidence	Recent and small, follow-up up to about three months	Longer history across several device generations
Typical plan at our clinic	Usually a short course, set at consultation	Usually a single session

A chart like this helps with orientation. The deciding factor is not on it: what your skin is doing, and at what depth, is read in an examination.

What the Evidence Does and Does Not Show

Thermage has been in use for more than twenty years across several generations, and there is a substantial clinical literature on monopolar radiofrequency built largely on it. Studies specific to the FLX generation include a Korean dermatologist survey on practice patterns and a 2025 study of upper eyelid tightening in Asian patients using the 0.25 cm² tip.

XERF’s published record is newer. It includes a prospective multicentre study in 39 people who had two sessions and were followed to 90 days, a retrospective study of 16 patients after a single session followed to three months, a periorbital technical report, and laboratory and animal work. These studies report improvement and only mild, transient reactions, and their authors describe the findings as preliminary. All of them have links to the manufacturer through funding, device supply, staff authorship or training roles, and none compared XERF with another device.

Two points are worth stating plainly. First, no published study has compared XERF and Thermage FLX head to head in patients, so claims that one gives a stronger or more durable result than the other are not established. Second, the two devices carry different US labels. Thermage FLX is cleared for the non-invasive treatment of wrinkles and rhytids, including the upper and lower eyelids. XERF’s US clearance is for electrocoagulation and hemostasis in dermatologic procedures. Regulatory wording differs by country, and neither label is a promise about any individual’s result.

Sensation, Numbing and Downtime

Both treatments are felt as pulses of deep heat. With Thermage FLX, Solta lists mild to moderate pain in the treated area as the most common effect during treatment, and the cooling and vibration are there to take the edge off it. At Dr. E-Laser Dermatology, a numbing cream is applied before either treatment. Sensation varies a great deal between people and between areas of the face, and because the devices have not been compared in the same patients, we do not rank them for comfort.

Downtime is short for both. After Thermage FLX, Solta lists redness that typically resolves within 24 hours and swelling that typically resolves within 5 days but can last several weeks. In the published XERF studies, the reactions recorded were redness and mild swelling that settled within one to two days. Less common effects are listed in our Thermage FLX in Seoul guide, and they are reviewed at the consultation.

How a Doctor Chooses Between Them

The decision starts with the skin, not the device. These are the questions that usually shape it:

Skin thickness and the depth of the change. A Korean survey of Thermage FLX users found that skin thickness remained the main factor in how well patients responded. Where the laxity appears to sit, and how thick the skin is over it, guides both the device and the setting.
The area. For the eyelids themselves, Thermage FLX has a dedicated eye tip and a US label that covers the upper and lower eyelids, which is why eyelid work is often discussed with Thermage first. For the cheeks and jawline, either device may be considered.
How you react to heat. Patients whose skin flushes or reacts easily sometimes prefer a plan where depth and intensity are adjusted area by area, which is how XERF’s depth settings are used at Dr. E-Laser Dermatology.
One visit or a short course. Thermage FLX is usually planned as a single session here. XERF is usually planned as a short course, which matters if you are fitting treatment around a trip.
What you have had before. Previous energy treatments, fillers, threads and implants all affect the plan, and the doctor will ask about each.

Sometimes the answer is neither, because the concern is structural sagging that points to focused ultrasound, or heavy laxity that no device will correct. Sometimes it is a staged combination.

Who Should Not Have Either

Some conditions rule out monopolar radiofrequency or call for caution. Solta’s safety information states that Thermage is not to be performed on anyone with a cardiac pacemaker or other active electrical implant, and that its use has not been studied in pregnancy or breastfeeding, over fillers, or in several medical conditions. The published XERF studies excluded people with pacemakers or similar devices, metal implants that could interfere with energy delivery, permanent fillers or facial implants, infection in the treatment area, and those who were pregnant or breastfeeding. Bring a list of implants, injectables, medications and skin conditions to the consultation, because these are checked before any plan is made.

Where Ultherapy Prime Fits

XERF and Thermage FLX are both radiofrequency. Ultherapy Prime is a different technology: focused ultrasound delivered at set depths of 1.5, 3.0 and 4.5 mm, including the SMAS layer, with live imaging used to confirm placement. When the main concern is structural, along the jawline, brow or neck, the conversation often includes ultrasound as well. Our Ultherapy vs Thermage guide compares the two technologies, and the non-surgical skin tightening guide maps the wider set.

If you’re already in Seoul and weighing XERF against Thermage FLX, share a photo and our English-speaking coordinators will help you plan what is worth discussing with the doctor. Speak with us on WhatsApp.

Choosing at Dr. E-Laser Dermatology

Dr. E-Laser Dermatology is a laser-focused dermatology practice in Cheongdam, Seoul, one minute from Apgujeong Rodeo Station. Both XERF and Thermage FLX are offered here, along with Ultherapy Prime, so the recommendation can follow your skin rather than a single device. The doctor reads where the laxity sits, sets the device, tip and depth to it, and will say so when a different approach would serve you better.

Our coordinators and staff support you in English, from the first message through the consultation with the doctor to aftercare. Our guide to finding an English-speaking dermatologist in Seoul explains the wider process. For each device in more depth, see our XERF treatment guide and Thermage FLX in Seoul guide.

Pricing and Consultation

Because a plan depends on the device, the areas treated and the number of sessions, pricing is shared during your consultation rather than as a single fixed figure.

Frequently Asked Questions

Is XERF better than Thermage? Neither is better in a general sense. Both are monopolar radiofrequency and work by controlled heating of the deeper skin. XERF adds a second, lower frequency and selectable depth settings; Thermage FLX has a longer track record. No study has compared them head to head, so the right choice depends on your skin and the area, assessed in person.

Is XERF the same as Thermage? No, but they are closely related. XERF’s FDA filing names Thermage FLX as its predicate device, and both use monopolar radiofrequency at 6.78 MHz. XERF also uses 2 MHz and offers three depth settings.

Who makes XERF? XERF is made by Lutronic, now part of Cynosure Lutronic, a medical device company based in Goyang, Korea. Thermage FLX is made by Solta Medical, part of Bausch Health.

Which hurts less, XERF or Thermage FLX? Both are felt as pulses of deep heat, and sensation varies between people and areas. A numbing cream is applied before either treatment here, and Thermage FLX also uses cooling and vibration with each pulse. They have not been compared for comfort in the same patients, so comfort is discussed at the consultation.

How many sessions do I need? At Dr. E-Laser Dermatology, Thermage FLX is usually a single session and XERF is usually a short course. The exact plan is set at the consultation from your skin and the areas treated.

Can XERF or Thermage FLX treat the eyelids? Thermage FLX has a dedicated 0.25 cm² eye tip, used with eye shields, and its US clearance includes the upper and lower eyelids. XERF has small tips that have been used around the eyes in published protocols. Whether eye-area treatment suits you is decided after an examination.

Can I have XERF and Thermage FLX together? Both are radiofrequency, so they are not usually stacked in one sitting. A plan may use one device and add a different technology, such as focused ultrasound or a skin booster, in sequence. The doctor sets the order and interval.

Is support available in English? Yes. Our English-speaking coordinators support you from the first message through the consultation to aftercare, and you are welcome to message us on WhatsApp beforehand.

About the Doctor

Dr. Kwangsuk Suh is a board-certified dermatologist and the medical director of Dr. E-Laser Dermatology. He is an adjunct clinical professor of dermatology at Kyung Hee University and Sungkyunkwan University colleges of medicine, and an active member of the Korean Association of Dermatologists, the Korean Association of Clinical Dermatologists, the Korean Society of Hair Restoration Surgery, and the Korean Society for Dermatologic and Cosmetic Surgery.

Arrange a Consultation

If you would like to know whether XERF, Thermage FLX, or a different approach suits your skin, we are glad to help. Share a photo, ask anything, and our English-speaking coordinators will arrange a private consultation. Speak with us on WhatsApp.

This article is for general information and is not medical advice. Outcomes vary between individuals, and a diagnosis and treatment plan are confirmed during an in-person consultation.