The progressive fork spring kit is designed to enhance the handling, road holding, and riding experience of your motorcycle. The progressive winding structure allows the spring to stiffen as the suspension compresses, with the springs working over their entire length to ensure a very high end-of-stroke stiffness (the fork does not bottom out). Supplied with HAGON fork oil (the high-performance additives used ensure perfect fork operation as well as optimal lubrication and protection). The fork spring kits + Hagon oil come with assembly instructions and oil level indications; the quantity and viscosity of oil are tailored to each motorcycle.