Learn what makes us great.

It’s more than the best cooling vest, more than the best cooling packs. Its the combination of the two that assures optimum performance.

All of our products are backed by a 60 day money back guarantee.

UnderCool, it’s a game changer.

What’s the point of owning a cooling vest if it’s bulky and uncomfortable? Get a vest you will actually want to wear. Designed to be worn discreetly underneath your clothes. UnderCool is comfortable and easy to use for every activity, day after day.

not all cooling vests are created equal.

Slim Profile allows you to wear what you want while keeping your cooling vest concealed.

Lightweight under 2 lbs. helps you keep your energy for the things you want to do.

4- Way Stretch keeps the cooling packs secure against your skin for optimal cooling.

88% Nylon / 12% Spandex

Breathable Mesh works with your body's natural cooling methods and whisks sweat away.

Machine Washable so you can use it day after day.

Adjustable straps keep your UnderCool comfortable and fitted just for you.

ThermApparel Advice: Sizing and Fit

Making sure your UnderCool fits like a glove will ensure the best cooling performance, check your natural waist size at checkout or get our complimentary fitkit measuring guide.

ThermApparel’s CoolPacks

Not Ice. Not Gel. Our Phase Change Material (PCM) cooling packs fit into pockets designed to conform to your lower back. Keeping the cooling concealed and comfortable. They are easy to use, ready to be frozen right out of the box, no need to soak or “plump” like other vests.

Engineered to work with your body.

Cooling packs freeze at 70°F (21C) so you won't cringe from the cold when you put it on.

Works great in dry AND humid conditions

Non-toxic, biodegradable

Completely dry. No condensation like wet, sticky evaporative cooling vests. 

Fastest recharge time. 30 min ice water. 45 min fridge. 60 min freezer.

Safe to use directly against your skin.


SlimCool Cooling Packs

  • Thickness: .37"  |  .93 cm
  • Weight Per Pack: 5oz  |  .14kg
  • Weight of Vest Garment and 4 SlimCool Packs: 1.3lb  |  .59kg
  • Cooling Time: 1-2 hours

ExtendedCool Cooling Packs

  • Thickness: .67"  |  1.7 cm
  • Weight Per Pack: 6.5oz  |  .18kg
  • Weight of Vest Garment and 4 ExtendedCool Packs: 1.9lb  |  .86kg
  • Cooling Time: 2-3 hours



ThermApparel Tip: The fastest way to recharge

You can put your cooling packs in ice water to refreeze them even faster than in the fridge or Freezer. It will take 20 minutes to fully freeze them this way.

Beat the heat. Without the chill.

Did you know UnderCool Cooling Packs freeze at 70°F / 21°C keeping you cool, but not cold, and allow a lot of ways to refreeze and store?

Refreeze quickly in a cooler of ice water for a cool 32°F / 0°C

Keep a cooler of ice water handy for a quick 15-20 min recharge.


Store in the freezer for a brisk 0°F / -17°C

Cooling Packs refreeze in 45 min. Safe to store in the freezer long-term, if not wearing right away, taking to an event, or needing the extra few minutes of cooling. 


Store in the fridge for a cool 40°F / 4°C

Cooling Packs refreeze in 60 min. Safe to store in the fridge long-term. Cooling Packs will be at a comfortable temperature to put on right away.


Store in A/C for a cool 68°F / 20°C

Cooling Packs refreeze in 8-12 hours. They may not feel cold to the touch but they are working to keep your core cool.

ThermApparels environmental difference.

ThermApparel uses a bio-based PCM which is non-toxic and bio-degradable. A great improvement over older technologies like toxic-paraffin PCM and salt hydrate gels.

All plastics used to encapsulate PCM will eventually wear out. Unlike our competitors, ThermApparel offers a recycling program to easily and safely replace worn-out Cooling Packs.

Questions about our vests or shipping? Reach out to the ThermApparel team toll-free at 855-232-7233, write to us through our website’s contact form or chat with us via live chat. We always respond because, otherwise, that wouldn't be cool.