Made of high material for durability and stability Pressure can be adjusted by springs or air (nitrogen); Operation of the coil- over springs and air cylinder is helpful to reduce the shock No instruction included, professional installation recommended The suspension leg provides a smoother ride and better shock absorption management. The spring seat is insulated from the spring to ensure a quiet and comfortable ride The suspension shocks struts provides a smoother ride and better overall damping management Specification: Product Name: Shock Absorber Color: Black/ Gold+Black Material: Aluminum+Iron Total Length: 390mm Eye Core Length: 360mm Eye Diameter: 12mm Eye Thickness: 20mm Spring Thickness: 7mm Spring Width: 60mm Working Stroke: 60mm Factory Air Pressure: 0. 4 Mpa Maximum Air Pressure: 0. 5 Mpa Air Reservoir: Adjustable Placement On Vehicle: Rear,Left, Right Fitment: Universal Motorcycle Eye To Eye Length 360mm. Package Includes: 2 X Shock Absorbers 2 X Eye Cores 2 X Adjust Spring Tools Note: This product is measured by hand and may have an error of 1-3cm, Due to the screen and lighting configuration, the colors may be slightly darker or lighter. This type of motorcycle shock absorber is designed to reduce the vibration caused by rough roads.