The Stacy Westfall Activity Ball can be used as an aid in training horses, a tool to help rider work on balance and improve seat position and as a horse toy that offers hours of enjoyment. A pump is included for proper inflation. Purple/Small: Approx. 26" height, 80" diameter. Blue/Medium: Approx. 33" height, 102" diameter. Red/Large: Approx: 41" height, 130" diameter. See balls for approximate circumference and height when fully inflated.