This is pack of four optional Tekno RC CNC Conical Shock Pistons. These shock pistons are machined from self lubricating POM material, with a unique and exclusive cone shape. These pistons are machined to perfection and have eight 1.3mm holes. Tekno recommends that these pistons are installed with the convex cone facing down for most track conditions to provide faster rebound and slower compression. But, they can also be run with the convex side facing up for extremely smooth, high traction tracks, but will limit the overall shock travel.