Wheelchair Accessories - 20" x 18" Rounded Bottom Wheelchair Cushion: 20" x 18", w/ Quadragel Pack This four-chamber gel insert provides increased support and comfort to ischial area. Quadragel also reduces skin breakdown, heat build-up and shear. The Support Pro Has a Rounded Bottom to Reduce Wheelchair "Hammock" Effect Add comfort and support to any wheelchair with the Support Pro cushion. The polyurethane cover is waterproof, easy-to-clean, and designed for pressure reduction. Comfort features include two-density HR foam, a waterfall front, coccyx cutout and a tapered, zero elevation design.