This light is grounded through the mount and has two wires

see pic below

the diameter of the body is 1-7/16 inch and the threaded portion is 13/16 inch diameter with a flat spot

and on—and simple wiring setup

Round Motorcycle Mirror - Perch Mount - Black with Retro Blue Glass Vendor_LC Manufacturing and Machine This light is grounded throughNeed that mirror to stay legal, or clear up a fix it ticket from the man? No billet, skulls, or LEDs here! This is a classic, compact 3" round motorcycle mirror equipped with blue tinted glass for a retro feel and to cut down on glare. This mirror can be adjusted and mounted on either left or right hand side. The stem is 4" long with 8mm x 1. 0 threads, the mirror is 3" diameter, and the whole assembly is black coated steel. Perch mount mirrors