Mattress: Get a half cap box semi orthopaedic mattress. Depth: Total depth of approximately 19cm which is designed to contour to your body shape. Bonnell spring: 13.5 gauge open coil spring unit. Firmness: Medium soft – perfect for side sleepers! Cover: Antibacterial and hypoallergenic mattress which features a cool touch cover. Sizes: Choose from small single, single, small double, double, or king size.