Coupling, trade size: 4 in, outside diameter: 5.38 in, Length: 5.38 in, flexibility: rigid and IMC, material: Malleable iron, connection: compression, standard: UL 514B, CSA C22.2 no. 18.3, CSA 065178 certified, NEMA FB-1, for joining lengths of steel EMT to rigid metal conduit or IMC