Those who enjoy the supportive qualities of a premium firm mattress will love the Serta Ellinwood mattress set. Utilizing Serta's 420 SertaFlex innerspring system, a unique offset coil design delivers optimal responsiveness to every contour of your child's body, resulting in a more personalized sleep experience. A layer of PillowSoft foam at the sleep surface cradles every curve, relieving painful pressure points for an uninterrupted, peaceful night's rest.