ProsourceFit Core Balance Disc Trainer, 14” Diameter with Pump for Improving Posture, Fitness, Stability $15.99 – $21.99 Make sure this fits by entering your model number. IMPROVE CORE STRENGTH & BALANCE – Strengthens and engages multiple core muscles at once to maintain balance during exercises MULTIPURPOSE – Can be used for working out or as a seat cushion to improve pos-ture and balance, rather than using a stability ball