Rigid to Enclosure Malleable Iron Insulated Threaded Hub 3-1/2″
https://nsiindustries.com/product/rigid-to-enclosure-malleable-iron-insulated-threaded-hub-3-1-2/
The Bridgeport 3-1/2″ Rigid to Enclosure Malleable Iron Insulated Threaded Hub securely connects threaded rigid service entrance conduit to a box or enclosure. The hub features a sealing ring to prevent contaminants from entering the enclosure.