It's a pillow...
I am one of those strange people that does not have an actual headboard. Instead, I have two of these pillows against the wall, then the two pillows that we actually use for sleeping are placed in front. I made my own covers for these; I think I made mine 27 x 27 in order to get a nice full appearance. Because of how our pillows are used (or not used, I should say), I can't comment on how well they stay firm or keep their shape. But, two of these are all you need on a queen sized bed.