Gronk Fitness Soft Plyo Box Set. 6" 12" & 18" - Commercial Grade Gronk Fitness Soft Impact Plyo Boxes are made from high density foam and covered with 18oz.vinyl Wide base so boxes will not tip - 30" X 36" - Most stable Soft Plyo on the market Each box has a handle for easy repositioning and Velcro strips for stability when stacking Built for Gyms Stack any combination together for desired height. Heights that can be configured : 6" , 12" , 18", 24", 30" and 36"