This is the Piston Pin for the O.S. 21XZ-R Speed Engine, OSMG2041. FEATURES: Steel construction INCLUDES: Piston Pin for the O.S. 21XZ-R Speed Engine (also known as a wrist pin) REQUIRES: Installation between piston and connecting rod SPEC: Length: .53" (13.5mm) Diameter: .16" (4mm) jxs 10/27/11 ir/jxs