Wheelchair Accessories - 18" x 16" Cushion Rounded Bottom Wheelchair Cushion: 16" x 18", w/ Quadragel Pack This four-chamber gel insert provides increased support and comfort to ischial area. It also reduces skin breakdown, heat build-up and shear. Support Pro Wedge Cushion Helps Prevent Forward Shifting Designed for the active resident, this cushion encourages proper posture and helps decrease pressure. When used with a reclining back, it helps redistribute pressure from ischial area to the back.