In reply to Dave the Rave:
I looked at that bag too, it's not apparent what rating Snugpak are using, I don't think it can be EN13537 which is now the norm. I have the impression that whilst Snugpak have sort of disappeared from the civilian outdoor market over the last couple of decades, they are a big provider to the MoD so I guess people in the military no the name. They aren't very expensive for the warmth, but that one that got mentioned above is literally twice the weight of a down bag I have that is a little bit warmer than their claimed warmth.