Sizes 40cm, *50cm, 60cm – TRAX™ Surface Prevents Slipping and Provides Neurosensory Stimulation – Burst-Resistant Design Provides Safe Balance Platform for Conditioning and Rehabilitation Exercises Saddle Waist (Dipped Center) Offers Support and Control Change Balance Challenge by Adding More or Less Air – Don’t Over Inflate Multiple Sizes Available. Inflation Pump and Guidelines Included