The thickness of the mattress is not directly related to whether the mattress is ridged. Because reducing the spinal pressure during sleep depends on the support force of the mattress, and the thickness has no necessary relationship with the support force of the mattress, especially the spring mattress. The thickness of spring mattress mainly depends on the arrangement of springs and the thickness of comfortable cushion, but the supporting force is determined by springs. For example, the famous KINGKOIL mattress in Jin Keer, USA, has a thickness of 23cm-50cm, which is suitable for everyone to choose according to the height of their bedstead.