Rigid To Enclosure Compression Connector 2-1/2″, Malleable Iron
https://dev.nsiindustries.com/product/rigid-to-enclosure-compression-connector-2-1-2-malleable-iron/
The Bridgeport 2-1/2″ Malleable Iron Threadless Compression Rigid To Enclosure Connector joins unthreaded rigid conduit to a box or enclosure. The seal is concrete tight without tape. The connection is secured via a screw on compression fitting.