Nerf Dog LED TPR Squeak Tennis Sonic Ball. The Nerf Dog Balls have been designed for small dogs and puppies and will keep them entertained for hours on end. Two of the balls are made of tough thermoplastic rubber, this toy will stand up to extensive chew sessions. And, they float. The other two balls are tough tennis balls. All of the balls are ideal for toss and catch sessions and also solo play sessions. All four balls are suitable to go in the Nerf Dog Tennis Ball Blaster for small dogs and puppies. Compatible with the Nerf Dog Tennis Ball Blaster for Small Dogs and Puppies 2 TPR Balls and 2 Tennis Balls in the pack All 4 balls squeak to give your pet hours of fun Available in 2 sizes: Small: 2" Medium: 2.5"