The Nexus four-bolt duct connection system is designed to provide a simple and effective means of connecting rectangular duct sections together. This connection system may be used on all rectangular duct from 14 to 26 ga, resulting in sealed joints with clean lines that are aesthetically pleasing. J flange is a hollow roll-formed section of galvanized steel, containing an integral sealant. The synthetic resin sealant has excellent adhesion to metal, is easy to work with, is non-flow to 180 deg F and retains its sealing properties indefinitely.