Shock - 13.5" - STX Performance (HD515) STX single-tube design, Monotube shock with internal reservoir, High-pressure nitrogen gas-charged, 46 mm piston diameter, Adjustable rebound damping, Hose-mounted hydraulic preload adjuster, Multiple spring rates available to accommodate a wide range of riders, Top-level comfort, rideability, and performance, Hard-anodized precision CNC-machined components, Low-friction shaft and sealhead design, Fully serviceable and repairable