The Prism Ideal Cushion is a seat cushion with a contoured base for individuals with low back pain, arthritis, pressure sores, spinal cord injury and circulatory, lower extremity or mobility disabilities, including people who use wheelchairs or mobility scooters. It is designed for users that require mild to moderate postural support and offers contours that are intended to promote correct seating posture. The Ideal Cushion has three distinct layers: a top layer of soft poly foam; a central layer of pressure-relieving viscoelastic foam; and a base layer of contoured, high-density polyurethane support foam to provide positioning. DIMENSIONS: (WxD) (16, 17, 18 or 20) x (16, 18 or 20) inches. The height is 3 inches on the sides and 2.25 inches on the rear edge. CAPACITY: 250 pounds. WEIGHT: 2 pounds. WARRANTY: Two year limited warranty on cushion; 90-day warranty on the cover.