ThermAparel an
Top Performer

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ActiveMSers Top Performer
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ActiveMSers Top Performer

ActiveMSers Advice If a vest remains in your closet because you are too embarrassed to wear it, well, then it is of zero help. So buy what you'll wear. Pay attention to the manufacturer's return policy - ThermApparel's is 60 days for a full refund less shipping provided the vest is returned in like-new condition.

not all cooling vests are created equal.

Works In Humidity

Works in all temperatures. Suitable for hot humid climates and hot dry climates.


1-3 Hours Cooling Time

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


Fast Recharge - 20-60 Min.

Refreeze with a freezer, refrigerator or container of ice water. No electricity needed!


Lightweight, Comfortable, Reusable

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


Slim Fitting, Easily Transportable

7 sizes and 2 colors. Adjusts to fit a wide variety of body shapes and sizes.


Safe Against Skin

Non-toxic cooling packs provide consistent cooling temperature that won't cause ice burn.


Sizing Guide

How to get the right UnderCool for you.

ActiveMSers Tip: To get the maximum cooling effect from a vest, it should fit snugly around your body. If it hangs loose, some of the cooling power will be lost as you'll only be chilling air and not your body. ThermApparel's vest must be sized properly to hug you torso and lower back.

completely invisible and totally cool.

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As seen on ActiveMSers

TOP PERFORMER: ThermApparel UnderCool

One frustrating fact of cooling vests is that they tend to be bulky, clunky, heavy, and most announce their presence like a 6-pound cyst growing out of your neck. ThermApparel is flipping the script and has designed a vest that is virtually completely hidden, weighs less than two pounds, and lasts longer than many of their larger, full-vest competitors. The UnderCool is ultra lightweight and stretchy, think sheer (and comfy) yoga pants, and comes in a range of sizes and two colors (back or white), cinching at the abdomen with Velcro. Perfect for sports, especially those that involve running. Cooling comes from four phase change (PCM) cooling packs that are inserted into the back of the garment—there is no cooling on the chest. We expected this to be a noticeable negative, but in our testing we still felt refreshed. And a huge side benefit of no cooling packs on the chest: there are no cooling packs on the chest so women (and men) of all chest sizes can wear this comfortably and stealthily. Expect the slim version to last 1-2 hours outdoors on a hot day, 2+ hours when worn indoors. The extended cooling packs add up to an extra hour of cooling power, and is a recommended upgrade.

Weight: SlimCool Packs - 1.3 lbs, ExtendedCool Packs - 1.9 lbs

No Compromises Needed

Our vests are long-lasting and ready to provide cooling relief for seasons to come. Never settle for less! With UnderCool, it’s all good.







Our Tech

Already have a UnderCool Cooling Vest?

Need a replacement vest or extra packs?

Click on accessories in the shop.

How to beat the heat

  • Cool it.

    • • Quickly charge the cooling packs in the fridge, freezer or ice water.
    • • Cooling packs provide 1-3 hours of oh-so-sweet cooling.
  • Wear it.

    • • Slip the cooling packs into the vest and wear under your outer layer of clothing.
    • • Before ordering, check out our sizing guide to find your best.
  • Love it.

    • • Take UnderCool for a spin in and out of the garden with our 60 day return policy.
    • • Rechargeable cooling packs mean you can look forward to gardening again and again.

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.