Packed down, these tiny booties fit into a stuff sack the size of a baseball, which was perfect for one van-living tester who, tight on space, could fit them into her sock drawer. In Montana, when temps in the (heated) van dropped to the low 40s, they were plenty comfortable, including on the unheated floor, when she got up to make coffee. She could even step out of the van and into the snow without compromising the Hot Socks’ Primaloft Silver insulation. On a cold backpacking trip, they slid onto our feet and into a sleeping bag all night far easier than any of the bigger booties in the test, which, combined with their packability, made them a critical crisis layer for our feet. $65; 5 oz, (sz. M); S-XL