Milliard OfficeFit Fitness Ball Chair A great alternative to expensive ergonomic office chairs with no complicated knobs or levers to operate. Works just like a regular rolling office chair, but an exercise ball replaces your seat. As you sit and maintain balance, your body will naturally straighten your back to keep its center of gravity. Bounce happily to music, stretch when youre bored, or exercise quietly at your desk as you type. Now thats multitasking! Includes inflating pump, 20in. exercise ball, and rolling base with locking bar and seatback.