Zinc-Plated Steel Raintight Sealing Conduit Locknut 4″
https://hotfix.nsiindustries.com/product/zinc-plated-steel-raintight-sealing-conduit-locknut-4/
The Bridgeport 4″ Zinc-Plated Steel Raintight Sealing Conduit Locknut securely fastens threaded conduit to an unthreaded opening in a box or enclosure in wet locations. This locknut features a PVC seal that creates a raintight seal.