1 Air Valve extender shift knob top is 1/2 x 13 common thread ****MUST BE OLD VINTAGE PIN STYLE OF SEMI TRUCK AIR VALVE **** Add shift knobs to your PIN air valve. fits 3/8 inch inner diameter ADD SHIFT KNOBS TO YOUR AIR VALVES Aluminum W/ Chrome plating Comes with Roll PIN When installing use gloves as threads can be a bit sharp. Tips To remove your old pin you can use a punch or a small star tool with hammer Use some painters tape or other tape to protect the chrome finish and make the hole in tape To install easier you can use a Channellock pliers just make sure to protect the chrome plating on other side with a cloth or mat from pliers teeth Install tapered end of roll pin into hole first. You may want to squeeze the pin a bit before install to help it go in better. You can also use a vice to squeeze roll pin a bit more to help it go in better before install. * Shift knob not included just to show how adapter works. We have many shift knobs in our other items you can use. . * We also have the screw on type air valve adapters for shift knobs as well if you check our other items