Lightweight, portable gym ball base measures 19.5" diameter and fits a 45, 55, 65, and 75 cm exercise ball. Use this base to stabilize exercise ball and prevent ball from rolling around. The base can also be used with Exercise Band or Tubing for dynamic workout. The base has 4 built in anchors and 2 grooves for exercise band and tubing. The ball stabilizer is a good tool for individuals with Autism Spectrum Disorders as the base gives extra support for those who have a difficult time with balance.