The Ortho-Rock is an extra firm mattress that comes in four sizes: single (3ft), small double (4ft), double (4ft6) and king (5ft), so you can find the right fit for your bed frame. The tufted, knitted fabric cover sits above a layer of 1000# microfiber and ventilated soft foam quilting, giving a breathable surface with a neat, tailored finish. Below this, a layer of support foam and cotton padding sit on top of the main spring core, a 22cm pocket spring unit made with 2.2mm wire that runs edge to edge for stable, extra firm support. The build is mirrored underneath with more cotton padding, foam quilting and a polyester fabric base. The materials used are hypoallergenic, and all our mattresses meet UK fire safety regulations. This is a one sided mattress and should not be turned over, though it can still be rotated head to toe for even wear.