To hell with the march of the penguins, it's the march of the ridiculously light gear that we're talking about. Sierra Designs enters the fray with the Vapor 15 sleeping bag, an ethereal sub-two-pound bag 15F rated bag that's sure to worm it's way into your backpack.
The Vapor 15 cuts weight by using a half-length 25" zipper on the left side with a Velcro keeper flap at the top, a 15 denier nylon shell and high quality 850 fill down carefully trimmed from royal French geese directly descended from the actual bird that laid the golden egg. The fit is close by design, especially the jacket-style hood that cocoons your noggin with a single drawcord adjustment. The one place there's a little extra room is the foot box, which is just where you want the space for stuff you want to keep warm in the bag with you.
Two pieces of webbing at the shoulder and hips lock the bag into your pad to ensure that you stay on top of things. Because of the zipper design you can't throw the Vapor open to cool down, but if you can deal with that you're rewarded with an insanely light bag that will comfortably go below freezing. There's even a beefy draft tube down the full lenght of the zipper, and with a decent pad temperatures in the twenties will be comfortable for most people, and layering clothing you already are carrying will let you hit the 15 degree lower limit. The Vapor compresses to just bigger than a quart bottle, so it disappears into your pack, and at less than two pounds at the end of the trail your back and your legs will thank you. Available in short, regular and long.