Trideer Exercise Ball Yoga Stability Ball Trideer Exercise Ball in charcoal gray. This heavy-duty yoga and stability ball is perfect for core exercises, balance training, and as an ergonomic desk chair. Made with anti-burst, non-slip PVC material featuring horizontal ribs for extra grip. Condition: Pre-owned and retains full structural integrity and air pressure. Keywords: gym equipment, pilates, core workout, pregnancy ball, office chair alternative, fitness…. $8.00 ship 2 lbs