Swivel Chair Gas Spring with Additional Depth Spring Action over the Entire Adjustment Range. Your back will thank you for it: For highly ergonomic seating, the STAB-O-MAT-AD gas spring from Stabilus provides very comfortable spring deflection properties over the entire adjustment range and in the lowest seat position, combining the advantages of the STAB-O-MAT variants ID and CD. An additional coil compression spring in the outer tube provides superior depth spring action. This spring is connected to the piston rod of the gas spring via a flexible coupling. When the piston rod is fully compressed, the coil compression spring performs the additional end position dampening of the column. The gas spring and the coil compression spring work together in all stroke positions, resulting in extremely comfortable, soft shock absorption when the gas spring is locked.