Span America Convoluted Foam Overlay, 1 Each Exercise & Physical Therapy 20 X 18 * The 16 7136 20 X 18 * The contoured design combined with the simple operation of the ISOFLO© Memory Control unit offers provides a new level of postural control and stability that has never been achieved in an air cushion * The contoured design positions the pelvis back in the wheelchair and centers the individual comfortably in the middle of cushion * The ISOFLO Memory Control unit locks air into each of the four compartments providing stability by minimizing side to side and front to back motion * Adjustable to individual Features an adjustment screw to customize rail angle to suit even the steepest stairs * Easily folds up to store out of the way and will not accidentally fall down causing an impace injuty * A machined precision tension fit hinge creates stable rock solid support * An excellent support option for sunken living rooms decks patios or 2 and 3 step stairs in garages * The P Made from high quality combustion modified polyurethane foam