The Sea to Summit Circuit Down Sleeping Bag zips shut for full warmth on a cold night, then wraps its zipper all the way around to open completely flat as a quilt once the temperature climbs. 650+ fill power Ultra-Dry Duck Down packs down small into its included compression sack, so the bag adapts to the trip without adding bulk to the pack. What Our Gearhead(R) Experts Are Saying:"I unzipped mine flat on an unexpectedly warm night and used it like a real quilt instead of fighting a half-zipped bag all night. The down never bunched up or left a cold spot, even folded open like that."