Thanks, but I need to correct a couple of things. The Thermolite EXTREME bag liner advertises 25 degrees, not 40, as I mistakenly posted. It's a fiber fabric, not mylar as someone suggested, and is advertised to be suitable to be as a warm weather stand-alone bag. Weight is advertized at 14 oz.

Hope this clears thing up. They do make a lighter version with less claimed performance (about 15 degrees I think and weighing about 8 oz.

Thanks,

J.