Meet the Tennis Tumble, the ultimate interactive puzzle toy for dogs’ development. Our Tennis Tumble promotes challenging, independent play for medium to large dogs. Featuring a hollow tube shape and a trapped tennis ball inside, test your pup’s smarts and see how quickly they can free the tennis ball. Recommended for medium and large dogs. Materials: Tennis Tumble: Natural Rubber Tennis Balls: Natural rubber core, pet-safe poly felt exterior Product Dimensions & Specs: Length: 3.86" Width A: 2.56" Width B: 2.48" Ball Diameter: 2.36" (about the same size as a regulation-sized tennis ball).