Cycle Engineers' Institute (CEI) / British Standard Cycle (BSC) tap & die set

Off center vent hole

and the aluminum washer / spacer keeps the squish right where you need it

Right side 3/8")

What's in the box:

Miller/ Vincent STOP Reproduction Tail Light Vendor_JRC Engineering Cycle Engineers' Institute (CEI) /These custom motorcycle STOP tail lights are a reproduction of the original made by Miller which appeared on HRD Vincent and Velocette motorcycles starting in 1947. It acts as a running light, brake light (STOP lights up when you brake) and it also features a clear lens to illuminate your license plate. 12 volt bulbs are included, you can also swap them out to 6 volt bulbs for older charging systems. The lens of this light measure 2 5 8" in diameter.