Rigid or IMC Conduit Set Screw Aluminum Entrance Cap 4″
https://nsiindustries.com/product/rigid-or-imc-conduit-set-screw-aluminum-entrance-cap-4/
The Bridgeport 4″ Rigid or IMC Conduit Set Screw Aluminum Entrance Cap serves as a connection point for service entrance wires. This threaded type entrance cap features three 1-3/4″ dia holes or four 1-1/8″ dia holes.