The Euro ball is a made of a softer rubber than our solid rubber ball, the softer rubber is easier for the dog to bite. The Euro ball is a bit lighter and easier to throw. This is the ball of choice with Europe's dog trainers. Assorted colors.Available Sizes:Medium - Diameter 2.5 in, circumference 7.5 in (Normal size reward ball)Large - Diameter 3.0 in, circumference 9.5 inNote: The large size ball is slightly larger than a tennis ball and the medium is slightly smaller. See the additional images.