Coil sprung: 19cm thick with open coil spring inners. Mattress: Get a semi-orthopaedic sprung mattress. Semi-orthopaedic: Medium firmness - plus contours to your body's shape. Five sizes: Choose between small single, single, small double, double or king sizes. Anti-allergy: Anti-bacterial with a hypoallergenic filling. Semi Orthopaedic Sprung Mattress | Small | Living Social