The heart of the ON chair is the Trimension®. This innovative system is based on the clever combination of a two-part mechanism, an extremely flexible seat and backrest construction (Flexframe®) and the use of Fiberflex for the backrest upholstery. Fiberflex is an elastic and breathable material that adapts to the contours of the back and sitting posture like a second skin. The Trimension® has two independently movable swivel arms that are connected to each other at knee height via a pivot axis. At the rear, they represent the freely movable suspensions for the seat and backrest construction, which are positioned near the hip joints. The arrangement of the pivot points corresponds to the natural movements of the knee and hip joints and thus promotes extremely natural movement sequences. During all these movements, the body's center of gravity remains between the pivot points and therefore in a stable and balanced position. The materials used are characterized by high mobility, elasticity and good seat-climatic properties, which ensures excellent sitting comfort without the need for additional padding. The forward and backward tilt angles of the seat range from +3° to -12°, while the backrest can be tilted up to 30°. Both the seat and the backrest can be tilted up to 13° to the side. The counter-pressure in each direction of movement can be quickly adjusted to suit individual comfort levels and is infinitely variable for people weighing between 45 and 120 kg.