CanDo® dynamic stabilizer base has 4 built-in anchors and 2 grooves for exercise band and tubing. Lightweight portable gym ball base measures 19.5 inch diameter and fits a 45 55 65 and 75 cm exercise ball (sold separately). Use base to stabilize exercise ball and prevent ball from rolling around gym. Use base with band or tubing for dynamic workout. Deluxe Stabilizer Base - for 45 cm - 75 cm balls