In addition, the couplings’ single set-screw inspection cover provides easy access to cables or conductors. The 4256-DC model joins two ½-in. EMT to one ¾-in. EMT, while the 4258-DC model joins two ...

Article 358 covers the use, installation, and construction specifications for EMT and associated fittings. As noted in Sec. 358.42, "Couplings and connectors used with EMT shall be made up tight.