Pair of YSS progressive fork springs for Kawasaki ER-5 motorcycle. The progressive winding of the fork springs guarantees a high response of the front fork compared to the standard, considerably improving driving behavior and road safety. At the same time excessive digging under load is prevented as the spring stiffness increases during compression. YSS fork springs are made of high quality silicon spring steel. This allows the wire thickness to be reduced, which makes the spring more active and thinner, but at the same time effectively prevents the spring from twisting. To minimize noise and improve oil flow in the fork, the springs are fully polished and ground top and bottom. YSS supplies this kit designed and built to fit the specifications of the model on which it will be installed. Diametro 30.5mm, Lunghezza molla 427mm - Stiffness 5.8-9.5 N/mm