Insulated Grounding Bushing, 3″, Malleable Iron with Lug
https://nsiindustries.com/product/insulated-grounding-bushing-3-malleable-iron-with-lug-2/
Use the Bridgeport 3″ Threadless Malleable Iron Insulated Grounding Bushing to terminate threadless rigid or IMC conduit to a cabinet with a locknut that features a plastic metaliner to prevent damage to wire insulation.