This is the only synthetic-insulated bag we’ve found that matches the loft, weight, and compressibility of a comparably rated down sack. The key is Mountain Hardwear’s proprietary Thermic Micro insulation, which testers found both more compressible and loftier than other synthetics. Plus, the baffles are welded rather than sewn, eliminating the cold spots that come from pinched seams and needle holes. Add a luxuriously fluffy “face gasket” and dual side zips that let you stick out both arms, and you’ve got one extremely toasty, user-friendly bag. 0°, 3.4 lbs;