HELPS KEEP YOUR BODY MOVING. Safco Zenergy Ball Chair provides an active seating experience that helps encourage good posture, core muscle strength and may help increase concentration. ENCOURAGES BETTER POSTURE. Designed with an anti-burst exercise ball and four legs for stability and durability, Zenergy offers the posture benefits of a yoga ball without the rolling. These benefits may include better balance and concentration. CHOOSE YOUR ALTITUDE. Each Zenergy ball chair lets you select one of two heights by installing just the feet for a sitting height of 20" or both the legs and the feet for a sitting height of 23" â both options are included. GREENGUARD Certified products are scientifically proven to meet some of the worldâs most rigorous, third-party chemical emissions standards, helping reduce indoor air pollution and the risk of chemical exposure to help create healthier indoor environments DIMENSIONS. Overall (Leg Option): 23"H x 22.5"D x 22.5"W.