The Stamina® X Adjustable Height Plyometric Box is designed to help you build speed, power, agility and endurance. The box is made of heavy-duty steel with a nonslip rubber jumping surface, and it adjusts to 4 different heights to allow you to progressively increase the intensity of your training. Workout guide included. Stamina X Adjustable-Height Plyometric Box Black - Hand Exer. Equip. at Academy Sports