KONG Air Dog Squeakair Tennis Balls are just what they look like 100% pure tennis balls made in the same factory, using the same materials as any high-quality tennis balls. Air KONG Squeaker units are hidden and covered by the tennis ball material. * Tennis balls with a built-in squeaker for added fun * Non-abrasive material will not wear down dogs teeth at all * Bright neon green color makes it easy to find Sizing Reference: X-Small Tennis Balls are 1.5" Wide Small Tennis Balls are 2" Wide Medium Tennis Balls are 2.75" Wide Large Tennis Balls are 3" Wide X-Large Tennis Balls are 4" Wide. Very Important: No dog toy is indestructible. Supervise your dogs use of KONG Squeakairs until you are confident they can be used safely without supervision.