The First Years Swing Tray Booster Seat Specification.. The 3 in 1 portable booster seat is a highchair, booster seat and a play chair all in one. Features Wide tray has raised edges to catch spills Tray adjusts to three positions Quick one hand release Attaches to most adult chairs Adjustable safety belt 3 different heights Seat back folds down for portability and easy storage High backrest for stability Security belts to attach booster seat to adult chairs Suitable from 6 months+