XRAY's T4 Aluminum Progressive Shock Insert Set is an innovative progressive shock system for touring cars that provides improved traction and steering characteristics. Shock insert has 3 triangle cuts and uses a piston without holes. The hardness of the shock is influenced not by the holes in the piston but with the insert. The insert is mounted into the shock with wider surface on the bottom of the shock and narrower on the top.

When the piston is at the bottom of the shock, it the damping is softer and becomes harder as the shock compresses. This means that the shock dampening is softer in the first part of movement and becomes harder as the car rolls. The shock inserts must be used with pistons without holes, and must be used both front & rear, only on asphalt. The same oil is used in these insert-equipped shocks as with standard shocks. The inserts are CNC-machined from premium Swiss 7075 T6 aluminum, and are black coated. The pistons are molded using special processes & composites to ensure roundness, while maintaining maximum stiffness and durability. The pistons are additionally precision ground.