controllable/lockable gas spring,gas lift: 1)suitable for feet and back of massage chairs 2) Suitable for various chairs controllable/lockable gas spring,gas liftSpecification : JKQ28/50-L-120-N (JL4005)Force : unfixedTotal length : unfixedStroke : 120mm (unfixed)Cylinder diameter :50mm (unfixed)Rod diameter :28mm (unfixed)We can accept your design. gas lift for office chair