Ideal for children transitioning into a "big" bed from a crib or toddler bed, or for those who prefer a firmer mattress, the Serta Coppel mattress set provides a firm, supportive sleep surface delivering quality, restorative sleep. Serta's 420 SertaFlex innerspring system uses an offset coil design for maximum flexibility and responsiveness in order to react and conform to each body's individual contours. Layers of Serta Support Foam and PillowSoft foam add pressure relieving comfort while maintaining a nice, firm feel at the mattress's surface. Serta Coppel Full Mattress Set5 Year Non Pro-rated Warranty