BOSU Core Sliders smoothly slide across multiple surfaces, including carpet, tile, and hardwood floor. Flip the Core Slider to the foam or smooth side depending on the surface youre on. The Core Sliders are great for toning your legs, arms, and core. [Amazon addition] Core Sliders actively engage the core and work great with existing fitness equipment like the BOSU Balance Trainer. Each Core Slider is 7 inches in diameter and designed to fit most hands and feet perfectly. Core Sliders can be used with hands, feet, elbows, and knees to target abs and core.