This is the ergonomic chair that promotes better posture and a stronger core through the constant movement of its spring-tension support stem. The flexible stem keeps the cushioned seat from remaining in one static position, requiring the body to remain ever so slightly in motion at all times. This “active seating” prompts sitters to adopt different postures during the day, which builds abdominal muscles, prevents joints from stiffening, and relieves the monotonous pressure on the discs of the spine. Both height and stem tension are adjustable, allowing users to optimize the chair’s range of motion as their muscles strengthen. Die-cast aluminum base with powder-coat finish and metal casters; foam cushion. Please specify Red, Blue, Gray, Orange, or Black. Supports up to 290 lbs. 22" to 27 1/2" H x 22" Diam. (28 lbs.)