The bonnell memory foam mattress utilises a robust bonnell spring unit a traditional spring system offering great support and stability the coil spring unit is topped with durable polyester wadding and a sumptuous layer of memory foamthe unique properties of memory foam allow it to respond to your body heat and mould to your individual shape the medium firmness level and density of the foam provides great orthopaedic support and will offer optimum comfort while you sleep this great value hy