This is a high quality replacement Bitubo YXB rear shock. Stepless spring preload adjuster. Easy to install and adjust. Dual spring design features a softer spring for initial comfort and a stiffer spring for a gradual feel under load. Floating piston design with nitrogen pressurization. Steel body with anti-corrosion surface treatment for superior durability. Steel pump rod with low friction surface treatment. High quality alloy upper and lower mounts, CNC machined with a strong, durable hard anodized black finish. Comes with installation instructions and preload adjustment tool.