Die-Cast Zinc Conduit and Fitting Locknut 4″, UL Listed
https://hotfix.nsiindustries.com/product/die-cast-zinc-conduit-and-fitting-locknut-4-ul-listed/
The Bridgeport 4″ Die-Cast Zinc Conduit and Fitting Locknut securely fastens threaded connectors or nipples to an unthreaded opening in a box or enclosure. Operators can fasten the connection from both inside and outside an electrical box.