Reviewed by Colin Davies - 22nd Nov, 2020 Lives up to the name Bought this as a just in case for winter camping but decided to try it a couple of times in temperatures around 5°C to begin with. Noticeable difference compared to sleeping without the liner. Very warm and comfortable. I'll combine this with my 4 season bag and bivvy and don't have too much concern about being out in - 5°C and still being warm. At 5°C it's bordering on too warm so only had it around my legs and feet. Packs down to next to nothing. A lot cheaper than other Thermolite® solutions as well.