Not a true Twin XL. The dimensions say 80 inches long. It's barely 78 inches long and somehow 1.5 inches wider than it said... if only they put that inch and a half in the length, then I would be happy. Just crossing my fingers it fits in the Twin XL bed frame i purchased.. This bed is meant to go in my spare for my adult roommate... hence buying an "XL" for the extra 5 inches over a child's twin size mattress. Also, this is the classic "you get what you pay for" scenario. Cheap/sparse springs make it almost hollow feeling.. if you get up by pushing up with your hand, you basically sink to the ground or frame. Barely a "euro-top", so thin. I think it's only a matter of time before the springs begin to dig into your back... Honestly, just pay the extra $$ and buy the real deal. I'll keep it for now as I'm sure returning is a headache... might try selling just to get some of my money back.