$39 Farm and Fleet...not sure what brand but the best (dryest, warmest) I have had. Much better than the sorrels I had a while back. IMHO most people buy a boot that is rated for too much cold. How many times have you snowmobiled in temps below -20 let alone -140. It's been my experience that the feet will sweat too much and then all the moisture causes them to be cold. A dry foot will be the warm foot. I am not a scientist, but dont over think this either.