Here's old-school ultralight: This armpit-length sleeping bag reprises a half-length sack once used by European alpinists for minimalist bivy nights. The synthetic-fill bag is meant to be used in conjunction with a puffy jacket, and is designed for the abuse of real-world bivies. The waterproof/breathable cover is seam-taped for total weatherproofing, and the seat and footbox are reinforced so you can wear boots inside, or throw it down padless on a slab of rock.
Suspenders and a perimeter drawstring keep the bag pulled up around your torso and closed. Our tester found it true to its rating when used in combination with a down sweater. He added, "It's so light and packable, I also used it to warm up on winter lunch breaks and to augment an ultralight bag." Just remember: An old-school bivy isn't supposed to be fun. $129; 1 lb. 2 oz.; 40°F