The Topstar Sitness 20 in gray is designed to automatically align your pelvis, making it easier for you to work at your desk. When you sit on the Topstar Sitness 20, you are welcomed by a pleasantly functioning gas spring. The stool encourages you to place your feet on the lower rubber foot ring, which helps to align your pelvis and spine. This relieves pressure on the intervertebral discs and brings the spine into its natural S-shape. The Sitness 20 from Topstar also features a continuously adjustable seat height with a top lift, and the seat itself is ergonomically shaped. The base is extremely stable and mounted on a patented rubber tire. The air pressure can be adjusted to your needs. The metal base plate is made of chrome.