Palumbo Patella Tracker Small Medium Stand Up Assists 20 x 16 * Single Scooter Accessories 20 x 16 * Single compartment cushion * 4 air cells provide prevention and healing relief from ischemic ulcers (pressure sores) * Maximizes pressure distribution blood flow and nutrient exchange as well as shock and impact * Conforms to the body s shape and adjusts to body changes over time * Includes cover * 2 year warranty 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 8 thick neoprene * Viscoelastic insert conforms and adjusts