Both my boys (age 12 and 14) picked this mattress, 1 in medium and 1 in firm. It fits the top of their trundle beds well, and they love them! Firm is not firm like you would think with an innerspring. Its more like a medium firm. I was so impressed with theirs, I bought another in a medium 9" for one of the trundles for my 16 year old daughter to sleep on while we redo her room, and I bought a firm queen 14" just now for my husband and I. My 16 year old daughter also wants me to replace hers with this mattress as we complete her room. Even though my current bed, an expensive sealy memory foam topped innerspring, is only about 6 or 7 years old... it did not pay to spend the extra for the name. We are not heavy people, I am in the 130s and my husband about 50 lbs more... but you can see our innerspring Mattresses is sagging a bit...they just used to last longer in general. I will be happy to get 5 years out of these for the price, and I welcome the comfort! My husband and I actually fell asleep on our son's firm the other day, and both woke feeling so good we decided we needed one even though we were going to wait another year or two for ourselves. I have always been picky about my bed and I have always been a brand name mattress buyer. (My very first adult "on my own" big purchase was a Serta lol, not a car, and even my couch has sealy cushions!) so as far as I am concerned, its quite the testament that I am changing out every mattress in my house for these!