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 Eye to eye length : 190mm Spring diameter : 6mm Mount hole ID: 8mm Total Load Compression: 450 lbs Note: This product is measured by hand and may have an error of 1-3cm, which is based on the actual product. If you have any questions, please feel free to email! This type of motorcycle shock absorber is designed to reduce the vibration caused by rough roads.