With this oversized backrest, you can provide your entire back with the comfort and support it deserves. The high-density, medical-grade, anti-allergenic foam will keep its shape to keep you comfortable for long periods of time. The elastic strap adjusts to fit any chair and holds the backrest firmly and securely in place. Full-size zipper provides easy access to the removable, machine-washable cover. The cover is made of 100 percent polyester velour cover.