AliMed® Solid Seat Insert™ (SSI) with Cover solves the problem of sling-seat sag by creating a flat, level sitting surface that can accommodate any positioning or pressure-relief cushion without buckling. Helps prevent sacral sitting and discourages side-to-side tilt for improved postural support, pelvic balance, and even weight distribution on both ischial tuberosities. Unlike boards commonly used to bridge sagging seat cavities that can raise the user too high and cause instability, the SSI's semirigid, self-cushioning closed-cell foam block with convex bottom and flat top effectively fills this cavity to achieve a flat sitting surface while maintaining a proper height. This allows the user to sit securely while keeping their feet properly positioned on the floor or foot supports. Wipeable, no-slip vinyl cover is waterproof for incontinence protection and is ideal for users who move and slide involuntarily. Attaches to wheelchair with rear safety ties for added security. Available in two widths: 16" and 18".1-1/2" H (at center)