A firm sleeping surface is provided by organic cotton layers, and ensures restful sleep for your little bundle of joy. The Serta Tranquility Firm crib mattress features firm, balanced support throughout with heavy gauge coils, corner supports, flex clips and full perimeter border wire. It features an easy-to-clean, laminated cover. Cover adorned with an adorable Serta sheep pattern. Measure 52.5Lx27.3Wx5.8D.