Progressive 465 Shock For Harley Softail Features State of the art high pressure gas monotube shock design Utilizes a large 46mm bore and deflective disc piston for precise damping 16mm hard chrome shaft rides on custom viton seals for low friction and leak free life The 465 is custom tuned for each application and is completely optimized for each bike, from the damping and spring rate all the way down to the jounce bumper 5 position rebound adjuster,tune for changing conditions & riding styles Threaded body allows for fine adjustments in sag Aluminum body and components Hard anodized finish 13.1 is standard length for Flhc and Fxfb models / 12.6 is standard length for Flde, Flfb, Flsb, Flsl, Fxbb, Fxbr, and Fxlr models.