Is it a Pillowcase or Stuff Sack?

The Therm-A-Rest Stuff Sack Pillow is an ultralight dual-purpose stuff sack that doubles as a pillow. Just remove your items from the Stuff Sack when it's time to sleep, turn the Stuff Sack inside out and sleep on the plush, comfy side. Stuff your puffy or some clothes inside the stuff sack for an instant pillow.