This 45cm anti-burst exercise SandLock Watershed Sandbox Ball is the perfect size for use with your SandLock Sandbox to prevent pooling of water by creating a rain watershed. It helps to keep your sand dry. It can also be used as an exercise ball while watching the children play in the sandbox. Recommendations From SandLock: 1 ball with a 5×5 SandLock sandbox 2 balls with a 5×10 SandLock sandbox 3 balls with a 10×10 SandLock sandbox Kit includes: 1 Green 45cm Anti-burst Exercise Ball with logo 1 Hand / Foot Pump for Inflating Ball 1 Plug for inflation hole