Looked at the picture, didn't read the full description... - Exped Bivy Booty

From the picture I assumed the Bivy Boot was insulated with a fine polyester down and they looked like the ticket for extra cold night 'round here (Northeast, has been below zero a few nights and my felt slippers weren't quite up (or down?) to it. These are over-slippers without the fine polyester batting. However, not so long ago a bought a pair of super thick felt boot liners from Mukluks...something dot .com that were so thick I couldn't use them in the boots I bought them for, so they had been warming a shelf in the closet... until the bivy booties arrived! It's a match made in slipper heaven- the felt liners fit perfectly in the bivies, and wah lah, perfection.
Campsaver would have taken them back I'm sure, but I had serendipity on my side. The Booty's are well made from ripstop nylon, come with insoles whose technology I haven't quite sussed, but they're good quality. The drawstring cinchers are clever- pull the main loop to tighten, and pull the smaller orange release tabs(?) for a dramatically fast loosening, as if there's a spring in there (there's not). Glove friendly, well built and the large could probably wrap a climbing shoe or lighter weight hiking boot if you're in the tent, cold and disenclined to take any clothing, gloves or footwear off. They do make an impressive crunchy sound moving around, but the howling wind and vibrating tent walls will drown that out.