The Soft Ankle Board for the Pro Fitter is an attachable accessory that provides a more stable surface for standing, upper body, and sitting core exercises. Attaches over top of the footpads to remove the independent action of the feet. The Soft Ankle Board uses a soft foam padding to create more difficulty than the Hard Ankle Board. Please note there are two sizes. Soft Ankle Board 2 fits Generation 2 Pro Fitter models. If you are unsure about which Pro Fitter model you have, please contact Customer Service by calling 1-800-FITTER1 for more information.