This is made to put under a twin mattress that is sagging in the middle. This has air bladders that are higher in the middle than at the ends , so it helps with a sagging mattress. we have 2 of these. One we used under a mattress for a short period of time before we ended up getting a whole new bed of off of KSL. It definitely helped. The other has never been used. I am asking $10 each or 2 for $17. We are a smoke free pet free home. Phone calls or texts please. Cash only. We do not take venmo. thanks for looking!