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explore the world

reduce fatigue

beat cog fog

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improve performance

reduce fatigue

keep your focus

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reduce risk

stay on schedule

maintain focus

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UnderCool works by absorbing heat away from your body in a lightweight, long lasting, and comfortable cooling vest.

how does it do that?

Unique Garment Design

UnderCool vest uses 4 way stretch for a snug fit and strategically placed cooling packs for comfort and concealability.


Advanced Cooling Technology

ThermApparel Cooling Packs take into account human physiology, freezing at the perfect temperature to cool your core body temperature and work with your bodies natural cooling system.


more ways to use

Cool it.

Keep your UnderCool in a cooler, fridge, or freezer to grab and go whenever you need it. 

Wear it.

Slip the cooling packs into the vest and wear under (or over) your favorite outer layer of clothing.

Love it.

Stay safe, stay focused, and feel better after work.

Trust in Us! 60 days to try.

If a vest remains in your closet because you are too embarrassed to wear it, well, then it is of zero help. Invest in your health and happiness with a durable, comfortable cooling vest. To prove it ThermApparel has a 60 day exchange/return policy for a full refund less shipping provided the vest is returned in like-new condition.

Womens and Mens Sizing

Use your preferred shop to get the best measurements for your perfect fit. The products are the same in each shop. To get the maximum cooling effect from a vest, it should fit snugly around your body.

“I was able to enjoy Walt Disney World.”


Recipient of Presidential Service Award and 2
time Congressional Medal of Service Award

ThermApparel Festival Bundle
Medium White, ExtendedCool Packs


Why cooling is important?

Our bodies are always producing heat. It’s up to our heart and blood vessels to get that heat away from our core organs. Using a cooling vest makes life easier on your heart to keep you safe and give you more energy for what you care about.

UnderCool is:




Slim Fitting, Easy Fasten

7 sizes and 2 colors. Adjusts to fit a wide variety of body shapes and sizes. No zippers or snaps.


1- 3 Hours Cooling Time

SlimCool Packs 1-2 hours cooling time.
ExtendedCool Packs 2-3 hours cooling time.


Machine Washable

Mild detergent, cold water, air dry


Safe Effective Cooling Temperature

Cooling Packs freeze at 70F/21C. Not too cold or too hot. Keeping you comfortable and working with your bodies natural cooling.


Lightweight, Comfortable, Reusable

SlimCool Packs Weight - 1.3 lbs.
ExtendedCool Packs Weight - 1.9 lbs.


Earth Friendly

Non-Toxic and Biodegradable cooling packs are safe directly against the skin. Our packs come with our unique recycling program.


Did you know?

UnderCool cooling packs freeze at 70F working with your body to improve cooling. Other products which use Ice or colder PCMS for cooling can cause blood vessels to constrict. This prevents the cooling from reaching other parts of our body, and can cause your core to actually heat up by preventing the flow of blood to your extremeties.

frequently asked questions

1. How do I find my correct size?

Currently UnderCool comes in 7 sizes XXS - XXL to fit a wide variety of body shapes and sizes, because "one size fits all" really isn't true. UnderCool should fit your body like a glove to give you the best cooling support.

Sizing is dependent on your natural waist measurement, not your bust, shirt or pant size. You will most likely wear a vest smaller than what you think. Not sure where your natural waist is or how to get the correct sizing? Check our sizing guide to get the correct UnderCool for you.

2. How long will an UnderCool keep me cool?

Cooling packs will stay cold for 1-3 hours depending on your level of activity and the ambient temperature. ExtendedCool Cooling Packs last 2-3 hours. SlimCool Cooling Packs last 1-2 hours. To learn more about the cooling packs check out our tech page.

3. What if the UnderCool doesn't work for me? Can I return or exchange it?

Yes. We have a 60 day return/exchange policy .

4. How do I recharge the packs?

Our Cooling packs are the easiest and fastest to recharge for their next use. The packs can refreeze in ice water in 20 min, in the freezer in 40 min, and in the fridge in 60 min. Nothing else from you is required. To learn more about the cooling packs check out our tech page.

5. What is the difference between ExtendedCool & SlimCool Cooling Packs?

We offer two different types of cooling packs depending on your needs. The SlimCool packs last 1-2 hours and are lighter and more concealable. The ExtendedCool packs last 2-3 hours but are slightly heavier and thicker. To learn more about the cooling packs check out our tech page.


“I enjoy working at my pub more with my cooling vest”


Proud owner of Coach and Horse Pub

ThermApparel Adventure Bundle
Small White, ExtendedCool Packs


four things to decide before you buy

Bundle your order and save.

Upgrade from an UnderCool to a Festival or Adventure to save on extra sets of Cooling Packs or an extra Vest Garment.


White or black, pick your color

If you wear more dark clothing order black. If you wear more light clothing order white. If you still can't decide, buy an Adventure and get both colors!


Correct fit = best cooling

A snug fit ensures optimal cooling. With 7 sizes XXS - XXL, you will be sure to find you perfect size.


Cooling time vs. weight

ThermApparel offers 2 cooling pack options. ExtendedCool lasts 2-3 hours and weighs 1.9 lbs. SlimCool lasts 1-2 hours and weighs 1.3 lbs.


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.