Outside diameter 23.8 mm Diameter of the piston hole in the fork: 13.8mm Total valve height: 14 mm YSS fork valves transform a conventional fork into a controlled feel with better contact with the road. CAD developed and hardened from extremely lightweight 606 T6 aluminum with 65 Rockwell. Finely adjustable and usable for almost any fork diameter. Thanks to a sophisticated system of holes in the valve, the flow of oil into the fork is modified so that the contact and feedback of the road are significantly more direct. This gives the driver safety and a feel for the road surface. Scope: on-road, off-road, racing and touring applications. Fork valves are preset for the respective fork diameter. A subsequent fine adjustment can be made by the amount of oil or other viscosity of the oil. Principle of operation: The YSS fork valve is inserted between the piston rod and the fork spring. It is important to know in advance the inside diameter of the immersion tube and the bore of the piston rod. Tuning of the fork valve is possible with a little effort after installation: The fork bridge must be loosened, the oil sucked from the fork and the fork valve raised. The adjustment screw can then be tightened or loosened in 2-turn steps using an Allen key. Please consider turning the upper screw first and then tightening with the lower stop nut.