Zinc-Plated Steel Vibration and Bonding Conduit Locknut 3/4″
https://dev.nsiindustries.com/product/zinc-plated-steel-vibration-and-bonding-conduit-locknut-3-4/
The Bridgeport 3/4″ Zinc-Plated Steel Vibration and Bonding Conduit Locknut securely fastens threaded conduit to an unthreaded opening in a box or enclosure in a harsh vibration environment. This locknut is corrosion resistant.