Ive used this multiple times in varying temperatures and I honestly feel that for whatever reason I stay warmer just using my bag than having this liner. Iv had others use it was well and the max I would say it adds is maybe 5deg to a bag. I pretty much just use it as a liner to keep my bag clean. Expensive for that ... Id look elsewhere if you're looking to add warmth to a bag. Just pack ext
This review was written in the old system and had content requirements that are different than reviews written today.