I'm a new forum member here so I thought I should state that the discussions on cold weather sleeping bags here were instrumental in my decision on buying some "gucci kit". I ended up ordering the Nanok SF endurance -25 bag for cold weather and the Snugpak Special Forces Combo kit (two bags in the kit) for not as cold temperatures. Being in the Infantry weight was certainly an issue but especially for the winter bag low temperature rating was essential and the info I read was that the Nanok bag was good and the stated temperature ratings were accurate. I've trained in NW Ontario where the temp went down to -50 and a normal (January) daytime temp may be in the -30/-40's so I need a serious winter bag, even with the Nanok bag I may need a good liner and/or wear extra thermal clothing but it sounds like a good piece of kit. Thanks to everyone for their insightfull discussions!