The BOSU Ballast Ball was designed to stay put and not wander during workouts. This ball has a six-sided surface design for proper alignment and positioning and has 2.5 lbs. of multi-dimensional load, which can provide a fun, visual effect and audible feedback during lifting, shifting, and shaking exercises. With the BOSU^® Ballast^® Balls, individuals can perform exercise progressions and dynamic drills that are not possible on a regular stability ball.