Forty Below® Bottle Boot™ 1 Liter

Did a winter overnight at -15°F and my water stayed slush-free all morning, which never happens. The neoprene sleeve is thick enough that it actually feels like a thermos for your bottle.

Took this out on a week-long ski traverse where temps dropped to -20°F at night, and my water stayed liquid until the last morning. The neoprene fits snugly around the 1-liter bottle and doesn't slide off even when I shove it deep in my pack. Money well spent for anyone camping in real cold.

I was skeptical a neoprene sleeve could make a difference, but the thick insulation really does the job—left my bottle out overnight at -15°F and still had liquid water for morning coffee.