When it comes to staying warm in really cold conditions, there's no need to split hairs - mittens are def the best, and the Arc'teryx Fission SV Mittens are about as good as they come. With a stretch shell of durable Fortius® 1.0, a double layer of premium Goat Leather at high wear points, a GORE-TEX® insert to keep the water out, and Arc' qualilty throughout, the Fission is a mitt on a mission.