I’ve mentioned the Brooks Range Elephant Foot Sleeping Bag in the past but it remains one of the simplest, yet effective items out there.
Designed to work in concert with a parka, the Elephant Foot Sleeping Bag covers your feet to offer full, to-toe coverage. It weighs 18 oz and is filled with 8.5oz of 850+ DownTek treated goose down for waterproofness. The 20D shell incorporates a foot box lined with 40D nylon for abrasion resistance yet maintaining minimal weight.
http://brooks-range.com/Elephant-Foot.html
