The GoFit Ultimate Burst Resistant Core Stability Ball is a fun, yet challenging way to stretch, tone and tighten your body. What makes the GoFit Ball so challenging? Unlike training on a stable, flat surface, the ball is a round, unstable surface, so you not only train the primary muscle groups, but also the smaller stabilizing muscles as well. The stabilizing muscles are small, yet very important muscle groups primarily used for balance, alignment and posture. The ball total body workout is very efficient, allowing you to see the results you want in a much quicker period of time. Combine the ball workout with the GoFit cardio vascular jump rope program and resistance tube training and you have a complete workout that can be done anywhere, anytime, and at a very affordable price. As a general rule, the exercise ball should be large enough so that when you sit on it, your knees bend at a 90 degree angle. The 65cm ball is recommended for most people height 5'6" to 6'tall. Suggested weight limit of 600lb. The burst resistant ball is recommended for persons who wish to combine light weight training with their stability ball workout. Comes with ball pump, 2 ball plugs and an easy to follow exercise wall poster. Also includes a 25-minute Linda Leene stability ball workout DVD. GoFit Stability balls are made of rubber and contain no Latex.