Jolly Mega Ball Designed for extra durability for horses of all sizes, this ball's anti-burst design can withstand up to 2,500 lb. of pressure. This allows you to inflate the ball to its full capacity without hesitation. The Jolly Mega Ball is available in two sizes and either size could be used with any size horse. The manufacturer has found that the large size is the most preferred. However, these were originally sized according to horse size. Medium in mind for horses between 10 and 15 hands, with the large in mind for horses 16 hands and above. Features: Anti-burst design Inflation information included Foot pump included (medium ball only) Jolly Mega Ball Cover sold separately (item #E005693) Item Specifications: Sizes/Colors: 30" Blue (Medium - 10 to 15 hands); foot pump is included with this size only 40" Green (Large - 16 hands and above); requires an air compressor to inflate as the foot pump is NOT included Note on Inflation: To check if your Jolly Ball has been inflated to full capacity, stand inflated ball upright and measure the height. The medium (blue) ball should measure 30" high and the large (green) ball should measure 40" high. If not the proper height, continue to inflate. It is important to know balls that are not inflated cannot be measured with accuracy, as the anti-burst material of the ball stretches out.