Zpacks

A hoodless sleeping bag with a three-quarter-length zipper run along the bottom instead of the side: closed around the back like a bag, vented like a quilt when the zip is open, and no draft tube because the zipper sits under you — which is how the Standard/Medium comes in at 18.8 ounces for a 20-degree rating. Zpacks publishes target loft (2.5 inches for the 20 °F version) and exact shell and down weights for every one of the twenty-one size combinations, which is more transparency about construction than anyone else in this catalogue offers — and no lab rating at all, which is less transparency about temperature. There is no hood: an elastic cord cinches around the neck, and Zpacks's answer for cold nights is a warm hat or its separate down hood.

Best for: Thru-hikers who want a closed back without a quilt's drafts and will wear a hat instead of a hood

The Classic bag with the back panel and its bottom zipper taken away and pad straps added — the same 13.7 ounces of down, the same 950 fill, half an ounce lighter. That half-ounce is the most useful single data point on this site about what a closed back actually costs on a Zpacks bag: almost nothing, because the Classic already puts no down under you and carries no draft tube. Neither has a hood. What you are really choosing between is a sewn-closed back that cannot gap, versus the freedom to stick a leg out and a strap system that holds the quilt to any pad.

Best for: Side sleepers who move all night and want nothing pinning them