This Serta full mattress set features a 420 queen coil count steel innerspring unit for proper support with a traditional firm feel and the box spring is made from heavy-duty hardwoods, high carbon steel and other quality materials that feature oversized side rails to provide additional support and security. A unique foam provides cushioning comfort while maintaining resilience for durable support at the sleep surface, while the Stable-Base Foundation provides consistent support across the bottom of the mattress and isolates the impact of partner movement for undisturbed sleep. Treat yourself to great sleep, night after night!