I bought this foam pad to put over an air mattress bed. It is absolutely amazing. My guests just loved it. When you lie down on it, you sink into the pad and the foam conforms to the body. Absolutely wonderful. I am using a second one over a very expensive, brand-name foam mattress that is way too firm. It is such an improvement. I would recommend getting this 4" topper if a firm mattress is a concern or to make a blow-up air mattress into a more comfortable guest bed. I would not recommend this for anyone who prefers a firm mattress.