... 6 rings spring high manganese carbon steel,heat monlding,natural palm fiber,anti-bacteria & acarid, high elasticity. Model: 5338 size: 180 ... is high elasticity and compressive stress.2. High breathability natural palm fiber,they have the characteristic of warm in Winter and ... without any effect of moisture.anti-bacteria and acarid3. Half palm mix half spring, so one side is hard the other ...