This 6-pack of extra balls pairs with multiple Castages ball track toys, including the fan favorites Tower of Tracks, Chase Meowtain, and Cheese Chase II cat track toys, in case the originals get lost or damaged. Colorful and the purrfect size for swatting paws, these balls will give your curious cat ample opportunities to use those natural hunting instincts to go after its "prey," chasing the balls around their favorite cat tracks. Cats and kittens cant resist the unpredictable ricocheting nature, especially when theyre bounced, rolled, and swatted. The lightweight ping pong ball style has a hollow inside and is made of durable plastic that allows the balls to speed along the tracks, withstanding energetic feline play. The balls can also be added to a cat ball pit like the Cat Condo Ice Cream Truck, providing continuous entertainment for your ever-demanding cat. SAFETY & CARE: When choosing a toy, make sure to choose the appropriate size for your cat. This toy is recommended for cats 12 weeks and older. No toy is indestructible. ALWAYS supervise your cat when using a toy of any kind. Inspect toys regularly for damage and remove if broken, or if parts become separated, as serious injury may result. For cats only. Keep out of reach of children. May contain small parts.