Cool head. Higher ceiling.
Your body quits before you do. Above 39-40C core temperature, your nervous system throttles your muscles to protect you: pace drops, heart rate spikes, and your head still wants more. That is not weakness. That is a brake.
KELVIN is a stick-on cooling patch for your neck. Peel off the film, stick it on and it activates automatically, so you keep your grip while everyone else fades in the second half.
Proof, not hype
Neck cooling works mainly through perception. It lowers the heat signal to your brain and delays central fatigue, so you push harder at the same effort.
- +10.5% distance. Runners covered 3,030 m with neck cooling versus 2,741 m without, in a heat time-trial. Source: Practical neck cooling and time-trial running performance, Eur J Appl Physiol
- The brake is central. Above 39-40C your nervous system cuts muscle efficiency to prevent overheating.
- The neck is the spot. High thermoreceptor density near large blood vessels makes it the fastest signal to your brain.
- Honest note: KELVIN improves performance and your sense of grip through heat perception and central fatigue. It does not claim to lower your measured core body temperature, and it is not a medical device.
For endurance athletes
Fuel. Hydrate. Cool.
Gels and electrolytes keep your engine running. KELVIN adds what they can't: more than 4 hours of cooling.
ENERGY GELS
Carbohydrates to keep your energy up on long efforts.
- ›Fuels your muscles with carbs
- ›No cooling effect
ELECTROLYTES
Salts and fluid to replace what you lose through sweat.
- ›Replaces sodium and fluid
- ›No cooling effect
KELVIN
A cold signal on your neck for more than 4 hours. Works alongside your gels and electrolytes.
- ›Peel, stick, it activates automatically
- ›4 hours cooling, guaranteed
- ›Nothing to swallow, no stomach load
How it works
Peel. Stick. Cool.
Peel off the film, stick it on, and it activates automatically. No towel, no melting ice.
Peel off the film
Peel the protective film off the patch.
Stick it on
Place the patch on the back or side of your neck, over the large blood vessels that carry the cold signal straight to your brain.
Keep pushing
It activates automatically and keeps cooling for 4+ hours. The cold signal lowers your head perception, so your brain gives the green light to keep working at the same effort.
FAQ
Before you race
The questions athletes ask us most before their first KELVIN race.
How long does a KELVIN patch cool?
With KELVIN, I guarantee at least four hours of cooling. In KELVIN’s own tests, cooling often lasted six to eight hours, but that longer duration is not an additional guarantee.
Do I need to activate the patch?
Cooling starts when you remove the protective film. Apply the patch and secure it with the sports tape along the sides; there is no element to snap or break.
Does the patch stay in place when it gets wet?
The patch uses water-resistant sports tape along the sides. This attachment is designed to hold it securely in place as you move and when the patch gets wet.
What does the patch feel like to wear?
KELVIN is thin and flexible, so you barely notice the patch as you move. Its shape and attachment are designed for comfortable wear throughout a long effort.
When should I put it on?
Before the start. Peel off the film, stick it on, and it activates automatically. It keeps cooling for more than 4 hours.
Triathlon: stick it on in T2, at the start of the run.
Is it allowed in races?
Yes. No rule in Ironman or Hyrox prohibits Kelvin - it's just you, a patch and a cooler neck. Bring your own spares and bin the used ones in the waste zones.
Kelvin has not been officially approved by any race organizer, so we can't guarantee it's allowed at every event. Rules differ per race and change each season, so always check your event's latest rulebook before race day.
Is it safe on my skin?
Yes it is. See Safety & ingredients for details on ingredients, testing and warnings.
Can I use it more than once?
Each patch is single use.
How does it compare to ice or a wet towel?
Ice and wet towels depend on aid stations, warm up or melt within minutes and leave you wet. KELVIN sits on your neck from the start and keeps cooling for more than 4 hours, with no aid station and no mess. See the comparison table further down this page.
Can I carry it in a gel belt or pocket?
Yes, a KELVIN patch is thin like sports tape and weights a couple of grams. Easy to carry with you.
How fast do you ship?
KELVIN ships from stock in our Dutch warehouse and is delivered in 3-5 working days. You get a tracking link by email as soon as your order ships.
Can I return it?
Yes, you can return KELVIN patches within 14 days unopened and unused.
How do I dispose of a used patch?
A KELVIN patch is single use only. You can throw it away via normal waste/bins.
4+ hours of cooling
Built to outlast your race
Stick it on before the start. It activates automatically and keeps cooling for more than 4 hours.
Marathon
42.2 kmCooling through the second half, when the heat and the fatigue stack up.
Hyrox
8 × 1 km run + 8 stationsCooling from the first run to the wall balls.
Triathlon
Swim · Bike · RunStage positions based on typical time per leg.
Ultra trail
50 km+ · 6+ hoursAt least 4 hours of cooling guaranteed, often 6 to 8 hours in our own tests. On longer ultras, bring a spare patch for a later aid station.
From the start line
Athletes on KELVIN
“PR on my first hot ultra. It kept me cool past km 60.”
“Sub-1:35 and a new PR.”
At 12 km, when it got hard, the KELVIN patch was still keeping me cool. It pulled me through the toughest stretch of the Rotterdam Half. Couldn't be happier with the result.
Compare
KELVIN vs the usual fixes
Ice, a wet towel or a cooling vest all cool you down. Only one fits in your race and works when you decide.
|
KELVIN
4+ hours | Ice | Wet towel | Cooling vest | |
|---|---|---|---|---|
| Weight | [X] g | Handed out at aid stations | Light, heavier when soaked | [Typical weight] |
| Timing | On from the start, cools 4+ hours | Only at aid stations | Only where there's water | Before the start only (pre-cooling) |
| Mess | None | Melts and drips | Drips, soaks your kit | Bulky, needs a freezer |
| Price per race | €6.90–€9 (10-pack to single) | Free at aid stations | Low | [Typical price, one-off] |
Indicative comparison. KELVIN price per race based on current pack prices.
Safety & ingredients
Safe to wear. Clearly labelled.
KELVIN is made for use on the skin during sport. Below you'll find the product safety information we are required to provide under EU law.
Product safety (EU GPSR)
KELVIN is placed on the EU market in accordance with the General Product Safety Regulation (EU) 2023/988 (GPSR). The product is intended for single use on healthy, intact skin by adults during sport.
Product identification: KELVIN Cooling Patch, type/model and batch number as printed on the packaging.
Warnings
The following warnings are shown on this page and printed on the packaging:
- Warning, e.g. for external use only.
- Warning, e.g. do not apply to broken or irritated skin; stop use if irritation occurs.
- Warning, e.g. do not open, puncture or swallow the cooling element.
- Warning, e.g. keep out of reach of children.