Sometime in the 1960s, someone had the idea to make a polyester-filled nylon blanket that would tie into your poncho to make a sleeping bag, and I hope they and their family are fabulously comfortable. This is the single best bit of surplus ever, hands down. It is lightweight, fast-drying, and phenomenally comfortable. It keeps you warm without overheating, somehow. Probably black magic, but personally I'm ok with that.
Originally these were a weird ERDL-like pattern that was a little purple-y. In 1990, they finally figured out how to print the M81 Woodland pattern onto the 100% nylon material that the woobie is made of without it looking like crap, so we did it. We used these clear into the mid-00s and I'm sure some reserve unit still has them somewhere. Probably one based out of Ft. Carson.
Size wise, this is a funky shape so its hard to describe. But its a little over 7 feet long and a little over 5'6" when opened fully. It has tie points at the corners and half way between those to tie into a poncho.