I have a Queen sized bed. It's a Sealy mattress and about 15 inches high. I got it in a "FIRM" and it's almost hard as a rock, but I love it for my back. I can "sleep" all over it at night. A single is just too small for tossing and turning and "sprawling" out when you want to. I absolutely love my bed and know it was one of the best investments I ever made.