The square hole distributes body weight evently and support without any pressure. Helps relieve pelvic, lower back ,tailbonea pain. You can sit in anywhere pain-free.Made from thickened flocking PVC, breathable & comfortable, durable. Note please clean the air seat by dry cloth, do not wash by washing machine.18"L x 15"W x 4"H. Great for using on wheelchair, bed, sofa, office chairs, kitchen chairs, car seat, or recliners. Also fits for incontinence patients, pregnancy, paralyzed patients, elderly etc.Inflate or deflate your cushion quickly and easily. Lightweight and portable design for your convenience to use it in anywhere.The inflatable air seat cushion provides comfortable and butt support, relieves pressure from stressed out muscle due to injury or seating pressure.