ZPacks takes what most retailers would call a "superlight" bag and chops the unnecessary bits. Off goes the hood, the draft tube, and on goes a small and light zipper. The bag weighs a mere 17.1 ounces on our scale, performs admirably below freezing, and includes the best stuff sack we've ever seen included with a sleeping bag. ZPacks sleeping bags push the fast and light performance envelope to the next level.
The only significant drawback to this bag is its fixed girth. Quilts have the advantage of being able to adjust to the amount of clothing you're wearing or to various body types. The ZPacks 20 Degree bag performs at the highest level in three-season conditions but doesn't provide the versatility of a quilt; all but the skinniest people it won't be able to accommodate a down jacket in the winter.
The Katabatic Gear Palisade is our highest rated backpacking sleeping bag and our top choice for one lightweight bag that can be used in both summer and winter temperatures. If you prefer a hood, consider the Feathered Friends Penguin but be prepared to carry an additional seven ounces and pay the extra cost of a more complex bag. Those on a budget can't beat the $100 Kelty Cosmic Down 20.
Also see our General Purpose Sleeping Bag Review and Winter Sleeping Bag Review.
The 20 Degree has had a few updates since we last reviewed it. Keep reading for more details!