Skillbuilders modular seating system allows for basic Feeder Seat to transform into floor sitter and mobile floor sitter. Each seat has built-in abductor, contoured interior for correct seating posture and a safety harness. Seats are made of molded foam that is firm yet soft to the touch, with integral waterproof coating that is easily washed for years of use. 2-piece mobile floor seat set includes seat and mobile box-type base with casters. Base includes pull strap. Seat is attached to the base with velcro for a secured fit. X-Large seat fits child 61-72" and 60-120 pounds.