Reinforced Chassis 4.2 Processed anti-rust steel 216 springs per meter. High quality sponge 14, 18 and 20 density. High quality Turkish double-layer cloth with two layers of thermal fiber. Four slots for ventilation. Two layers of felts to ensure the quality of the mattress. All sizes and dimensions are available. Super soft sleeping technology; determined for long term usage. Ecofriendly and odourless adhesives.