This is an option part for short shock for IF15/IF15W. 3 hole - 0.9mm piston. (3 hole - 0.9mm and 2 hole - 1.1mm piston is also available. This piston is secured with an ultra small screw as used in the IF14-2 to increase stroke. A dedicated 0.05" inch size tool is required. (A0100) INFINITY 0.05" hex wrench driver.