Experience the best of Beautyrest with the Black Series Four 17.5"" Firm Pillowtop Mattress, featuring advanced temperature management technology, Micro Diamond Memory Foam, Self-Response Latex, and advanced, Triple-Stranded Pocketed Coil Technology for conforming support and motion separation. Two layers of 2K Nano Coils, for a total of 4K Nano Coils, offer a specialized upgrade as they conform to your body for enhanced, individualized support. With the inclusion of 4K Nano Coils plus additional layers of premium foams, the Series Four model is the most exclusive offering in the Beautyrest Black Collection. With the inclusion of premier materials and advanced sleep technology, this Collection optimally aligns at the intersection of luxury and innovation for an extraordinarily comfortable sleep.