Fit-Chair 40090 with Base Ergonomically designed ball fitness chair for improving posture Provides healthy, proactive sitting position that engages muscles Encourages minor motions for better balance, stability, and strength Improves circulation so you can sit without back stiffness or fatigue May burn up to 35 extra Calories per Day Ergonomically designed ball fitness chair for improving posture Encourages minor motions for better balance, stability, and strength Improves circulation so you can sit without back stiffness or fatigue May burn up to 35 extra Calories per Day Ergonomically designed ball fitness chair for improving posture Provides healthy, proactive sitting position that engages muscles Encourages minor motions for better balance, stability, and strength Improves circulation so you can sit without back stiffness or fatigue May burn up to 350 extra calories per day