Penske Racing Shocks offers this 20mm fork piston and shim kit for most fork inserts. Using our successful velocity dependent piston design to separate low and high speed velocity, this kit will transform your street performing forks into track ready racing forks. You will be amazed at the difference you will feel by simply installing new pistons and shims into your forks. This is a must have if you plan on taking your bike to the track or if you plan on replacing or re-valving your rear shock.