Bial EX Stability Disc for Fitness and Balance Exercise with Pump Size: 13" diameter; Shipping weight: 2 lbs Pre-inflated to a level suitable for most uses: standing, kneeling and sitting & push up to develop balance & stabilization Balance disc promotes core stability, strengthens muscle tone, improves balance and body posturePopularly used as a child's "wiggle seat" to help calm anxious kids Balance cushion provides an unstable surface to exercise on, requiring you to use more muscles to stay balanced. Knobbed top surface for tactile stimulation and smooth bottom surface