I just bought a WM Ultralite 6' bag. Marketed as 20 degrees, 1 pound 10 ounces. It replaces my 6'6" 15 degree 2 pound bag. Saving 6 ounces and giving up only a slight amount of warmth looked good to me. Thing is, the WM bag weighs one pound, 13.3 ounces. Less than half the weight savings I expected. This pisses me off. So the moral is: Don't trust; verify.