Tri-Zone Pocket Coil System – Includes 3 zones of support at 1322 coils (head/torso/foot) with thick 2-mm spring coils for extra lumbar support in the torso zone. includes a 1-inch viscose foam with 20-0z hallow fiber. Foam Encased Edge Guard – 4-inch hard foam perimeter for added edge/sitting support, with a ½-inch quilted border. Pillow Top Comfort – flippable mattress with 2-inch medium soft foam pillow top with double fiber pad for added lumbar support. Bamboo Woven Fabric – Stretchable silver bamboo woven fibers for natural comfort and hygiene.