Gaiam Essentials Balance Ball & Base Kit, 65cm Yoga Ball Chair, Exercise Ball with Inflatable Ring Base for Home or… $27.30 – $32.93 Make sure this fits by entering your model number. EXERCISE BALL CHAIR: This 65cm balance ball works great behind a desk in the office as well as at home as a yoga or stability workout ball INFLATABLE RING BASE: Ball chair stays in place and will not roll away with the base kit – balance ball and base are not connected and can be removed for ball only workouts