Unstable stepping surface will tilt, twist and spring back as it reacts to the body?s movement. Improve core stability and overall proprioception. Use for standing, lying, stepping and for functional upper body movements. Incorporate with medicine balls, aerobic bars, tubing and dumbbells for more advanced drills. Plastic top with rubber slip resistant cover has eight notches to accommodate resistance tubing. Steel base has rubber feet for added stability. Color: Black. Dimensions: 29" L x 22" W x 6" H. Wt. 33 lbs.