Why It's CoolThis one-pound-three-ounce bag has no hardwareno zip, no Velcrojust a single cinch clasp on the hood's drawcord. » The Beeline is rated to 30 degrees, thanks in large part to the 900-fill goose down's impressive loft. » Shaving additional grams is the Pertex Quantum fabric used in the liner and the shell. » Because the bag seals in warmth so efficiently, I stayed toasty even on New England nights that dipped five to ten degrees below freezing.Hmmm . . .The zipperless construction doesn't seem quite so nifty when you have to extricate yourself to answer nature's call.