The Jay Zip cushion has a dual-layered foam base that combines structural support and comfort. Typically, a child using an 8" wide cushion may require slightly softer foam than a child using a 14" wide cushion. For this reason, the firmness of the Zip's foam base increases with the cushion width. 3DX spacer fabric in the outer cover also promotes air movement to prevent heat and moisture build-up. Maximum user weight 75Kg.