Key memory foam 10" twin mattress by Coaster NEW SPECIAL ORDER CO-350064TRetail price $473. Special order only; usually takes 5 14 days to come in. Thick memory foam padding gives this twin size mattress a spectacular sense of contour conforming coziness, while a base of high density foam provides dependable support for long lasting comfort. The hallmark of the Key Collection is the durable construction and quality material composition, allowing you to feel confident investing in this piece for any member of your family.