The SPRI® Ultraball™ has superior performance and maximum durability which help make it the safest and most reliable stability ball on the market today. It's made of a heavier, thicker-gauge material than other balls, so it's more resistant to stretching or deforming and ideal for use in the most demanding club environments. The dimpled surface offers a 360 degree body-traction effect. Slow-deflate anti-burst technology up to 600 lbs. Choose between 55cm or 65cm. Includes a free downloadable exercise guide. Does not include an inflation pump. SPRI® Ultraball™ Features: Superior performance and maximum durability Safest and most reliable stability ball on the market today Thicker-gauge material Resistant to stretching and deforming Ideal for the most demanding club environments Dimpled surface for extra traction Slow-deflate up to 600 lbs. Downloadable exercise guide