This is an option part for short shock for IF15/IF15W. 1 hole - 1.3mm piston the same size as used for IF18-2. (3 hole - 0.9mm 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.