This is a must for everyone who wants to do YBR®. It is a softer edge and has more give so that when you press into it, it supports you without a hard edge. This is the ball we recommend most for doing all abdominal, chest, and sideline work. It is also recommended for the Save Your Lower Back DVD and for the YBR® and Pregnancy DVD. Anyone with osteoporosis, fibromyalgia or rehabbing from surgery or an injury should also start with the Gold ball.