Ishara Neck Pillow, Comfortable Memory Foam Neck Support Travel Pillow for Airplanes

The pros: Inexpensive, the cover comes off and is washable and it comes in a nice storage bag. Cons: the back part, where you rest your head, is too thick. It was not comfortable to use behind my head on the airplane. At all. I ended up sleeping bent forward and leaning my forehead on it against the seat in front of me. This did work ok as it blocked out the light and was still able to breathe since my face was in the middle of the donut shape... but don't plan on reclining comfortably with it behind your head.

perfect!