The 13” x 12” x 6-3/4” booster features an adjustable spring system that allows it to fit any four-legged chair (round or square legs). It requires no assembly, snaps onto chairs in seconds and stays attached even when the chair is moved. It also features non-slip, rubberized feet that will not scratch floors. The booster’s height can be adjusted to grow with each child. This item is intended for children between the ages of 20 months to 6 years, and weighing under 300 lbs.