Yes4All Toning Ball (Marble/Diamond Grip/Smooth) – Soft Weighted Medicine Ball for Pilates, Yoga and Fitness $10.50 – $24.99 Make sure this fits by entering your model number. BUILD STRENGTH, BALANCE & COORDINATION: Yes4All toning balls are perfect for balance, flexibility & strength workouts. Performing exercises with an unstable ball engages your body’s deepest stabilizing muscles for coordination & maximized strength PVC SHELL – UNSTABLE IRON SAND INSIDE: Made of PVC and filled with natural sand, our toning balls are durable to function well for a lifetime. Natural sand inside creates instability to activate different muscle groups for a leaner & tighter body