This is the old style cap and not suited for X2 models.

Hint! If nothing happens when the cap is turned and it wont go softer or harder its probably the adjustment screw that is damaged and not the cap. First make sure that you feel under the needlebar pin and not over when feeling the adjustment. If you cant change the softness by turning the cap its probably the hexagon on the adjustment screw that is damaged. This can happen when it is tightened to hard in the bottom. If this is the case you need to purchase a new adjustment screw.