Circular stretch cover with Lycra provides a snug and breathable fit and helps protect the mattress from wear and tear, spills, and allergens. TheraSponse Foam provides excellent support, extreme durability and comfortable sleep surfaces for years. TheraCoil Open Coil Innerspring provides the ultimate in comfort, durability, and flexibility for the longest lasting sleep. TheraFoam encasement provides tremendous edge support for a smoother transition in and out of bed.