FS 2 poly sleepsacks
These are brand new and have the original $19.95 sales sticker. They are also referred to as travel sheets and are like a soft, lightweight sleeping bag.
They are made of 70% Micro Denier Polyester/30% Micro Denier Viscose but feel like a very soft cotton. Made by Sleep Innovations.
The French Navy one (sort of a dark bright blue/lighter than dark navy) is a regular Twin size. The white one is an Extra Long Twin.
They come in their own stuff sacks with an integrated pillow case and elastic straps (which I cut off) to go around a mattress. You could put a drawstring at the bottom to make it easier to exit a hammock and/or walk around while wearing.
These are great for summer use or as a sleeping bag liner.
similar to this: http://www.campmor.com/outdoor/gear/Product___41673
$15 (each) shipped to lower 48.