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Need extra cooling?
Add an extra set of cooling packs to your UnderCool!

This Purchase Includes:

  • 1 set of cooling packs (4 individual packs)
  • Choose from SlimCool (the original, lasts 1-2 hours) or ExtendedCool (lasts 2-3 hours)

Non-toxic, biodegradable, FDA approved phase change material
Safe on skin. Won't cause ice burns like ice or some gel packs.

Quickly refreeze in 20 min in ice water, 45 minutes in freezer, 60 min in fridge
Cooling relief for up to 1-3 hours depending on type of pack selected

Easy to use: No need to soak or "plump" in water before freezing and can stay in your fridge or freezer for an unlimited amount of time between uses.

Care and Storage Recommendations:

  • When not in use always store Cooling Packs in a solid state, this means the fridge, freezer, or a room less than 70F/21C
  • Cooling packs left in a melted state for extended periods of time will result in rapid aging and reduce the lifespan of the cooling packs.
  • When handled properly packs should last 2-3 years, and our recycling program provides deeply discounted replacement packs.
  • To wash your cooling packs, use warm soapy water in the sink. Do not put them in the washer, dryer, or dishwasher.


Please review our Return and Exchange Policy and our Warranty Policy.


Consult your doctor or health care professional prior to using this or any cooling products for a medical condition. ThermApparel LLC will not be liable for injuries or damages resulting from the misuse or misapplication of our products.

*Cooling times may vary depending on your level of activity and the ambeint temperature. 

Please Note:

  • All prices listed in USD
  • International orders: your country’s taxes and duties are NOT included in the price or shipping

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.