OKWU COMFORT 4 Inches Thick Coccyx Orthopedic Pressure Relieving Memory Foam Seat Chair Car Pad Cushion Non Skid Slip, Black Large Thick Firm 18x16x4 High-density memory foam that reduces pressure on the coccyx, tailbone and hipbones while sitting. Great for traveling in cars, planes, trains, buses, wheelchair, office chair, bench, Starbucks, patios, sport games, chairs, and outdoors. Ergonomically and patented design promoting healthy weight distribution, posture and vertebral alignment. Promotes comfort, assists in relief and avoiding lower back pain, numbness, and pressure sore. Reliable material and cushioned foam with removable velour cover machine washable and allows for easy cleaning. Removable and washable cover; 5 year warranty