I got one of these for review years ago from Snugpak as part of their KWART sleeping system, which consisted of the Kestrel, a fleece liner, and a proofed Pertex bivi bag. I'd rate the Kestrel at 2 Seasons, warmer with a liner. It takes up about the same space as a 3-4 Season down bag. I gave the Kestrel to my youngest daughter when she was small. She's 19 now and it's still going, gets used a few times a year for camping, and for when friends stay over. It's OK, but I think there are much better bags around.