INDOOR | 4 in Octagon Back Plate With 3/8 in Fixture Stud; (2) 1/2 and (2) 3/4 in Knockouts | 7 in Length X 1.26 in Width X 4.51 in Height, 17/32 in Dia Hole, for Rigid Conduit and Imc | Use Through Knockout to Connect Box to Conduit Coupling; Use With a Locknut to Connect Two Boxes Side by Side or Back to Back; Use With a Locknut to Connect Fixture Housings in Continuous Runs; Rigid Conduit Threads (Nps)Furbay Electric Supp