"What do I need to decide before ordering one of these?" Here are four things to decide before ordering your ThermApparel Cooling Vest.


 1. SIZE

Why is size so important? Easy answer, the size determines how it works. With 7 sizes XXS - XXL, ThermApparel Cooling Vests are made to fit a wide variety of body shapes and sizes, because "one size fits all" really isn't true. UnderCool needs to fit your body like a glove to give you the best cooling support.

If the vest is too big, the cooling packs seem "floppy" or the vest doesn't seem tight, you won't get the optimum cooling, the cooling packs won't feel cool and they won't last as long. The cooling packs work by direct and FIRM contact to the body. 

ThermApparel Cooling Vests don't fit like a standard shirt. They wrap around you in a firm but comfortable way to transfer the cooling to your core.

Most of us buy shirts that fit in the shoulders, neck, and hip area. UnderCool fits at your natural waist, this is the area below your ribcage but above your belly button. Think of how a cumberbund or corset fits.

For easy sizing guidelines watch this fantastic video with Julia or we can send you a free FitKit, that comes with a measuring tape and sizing tips. 

Once you have your natural waist measurement look at the sizing chart to find your size. If you are in between two sizes go with the smaller size.

For men the rule of thumb is one size smaller than your t-shirt size.
For women the sizing doesn't have anything to do with your bust or hip size. You will wear 1-2 sizes smaller than you normally do. 
Don't worry if you need help with sizing, call us 855-232-7233, or you have 60 days from date of purchase to exchange it for a different size. 


Can't decide? Because it is an undergarment, ask yourself, "what do I wear more of? Dark or light clothes? 

  • If your wardrobe is mostly dark clothing order a black vest. 
  • If your wardrobe is mostly light clothing order a white vest. 
  • If your wardrobe is both dark and light clothing order an Adventure Bundle, it comes with an option for a black and white vest. 

One common question: Is the white vest cooler? White will reflect more sun if the white vest is the outside layer. However ThermApparel Cooling Vests are designed to be worn under your clothing directly against the skin, so the color doesn't matter in regards to heat reflection. If you intend to wear your ThermApparel Cooling Vest on the outside or you clothing, please consider heat reflection and go with what works best for your area. 



We now have 2 cooling pack choices. It's simple. One lasts longer than the other. SlimCool Packs last 1-2 hours of oh-so-sweet cooling time and ExtendedCool packs last 2-3 hours of oh-so-sweet cooling time. Think about what activities you intend to use your ThermApparel Cooing Vest for and how long it takes to complete the activity. If you are going for a short walk use the SlimCool Paks, if you are playing a Golf, go for the ExtendedCool Packs

Examples of choices.

  • I am going to be sitting most of the time. Slim Cool
  • I am doing hard aerobic workouts. Extended Cool
  • I go for a short walk each day. SlimCool
  • I am going to hike for the morning. Extended cool

What is the difference other than time? The ExtendedCool packs weigh a small amount more. 
The Vest with 4 SlimCool Cooling Packs weighs 1.3 lbs
The Vest with 4 ExtendedCool Cooling Packs weighs 1.9 lbs.


It's FREE!
UnderCool bundles ship free with USPS Priority Mail. 
Festival and Adventure bundles ship free with FedEx 2 Day Express.  

If you need it as soon ASAP, FedEx Express and USPS Priority Mail Express are available for a charge. 


Try out your ThermApparel UnderCool cooling vest. for 60 days! And when we say try it out, we mean try it out. Go to the ball game, go to the gym, play with the kids, garden, skydive, go horseback riding. Do any and everything you can. Put the vest to the test!

Need to try a different size? Give us a call 855-232-7233 and we will set up an exchange for you. 
That's all there is to is. Please let us know if you have any other questions or ideas. You can always reach us via live chat, email and phone.
livechat - www.thermapparel.com

play cool. stay cool. be cool. 😀





From our humble origins we have been striving to help people live active, comfortable, and safe lives. In a time like this we all need more help and we hope this information on masks and the pitfalls of their use can help.  Remember that if you are overheating you can also make sure to stay a safe distance from others to remove your mask and take water breaks and switch out your cooling packs.

Stay safe, stay healthy, stay happy.

Julia, Kurtis, Brad

 is a small business making big waves in the heat sensitivity world by designing the first lightweight, comfortable and invisible cooling vest, UnderCool. Check us out online, on our blog, or on FacebookTwitter, PinterestLinkedIn and Instagram.

Please let us know if you have any other questions or ideas in the comments below, we will follow up. You can always reach us via:
Live Chat - www.thermapparel.com  |  Email - contact.us@thermapparel.net  | Phone - 855-232-7233 |  Address: ThermApparel LLC. 125 Tech Park Dr. Rochester, NY 14620

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