If you want the best quality, this Hop Series! This hop is the best quality of the hopping ball. Made to be very sturdy and durable. Perfect for indoor playground equipment. It will help you develop your body coordination and sense of balance while having fun. Hops come in three sizes. A W action pump that allows air to enter in either a push or pull. Important: The transparency may differ from lot to lot. Also, since it is transparent, oil stains may be visible and air bubbles when molding inside the molding, but this is not a defective product.