Soft Wood Plyo Box w/WeightShift Technology - Xtreme Monkey Get the MOST STABLE 20", 24" and 30" tall plyobox, all in one - Unit Weights 75lbs Durable Wood Interior Core w/ Multi-Layered Foam - Double Stitched Vinyl Upholstery WeightShift Technology - 3 Ballast Balls in the Core to eliminate shifting and tilting - Patent Pending Reduce injuries and get longer use out of a plyo box.