Outlet Boxes,Cvrs & Bar Hgrs | Conduit | Knockout Code (A): 1/2 In; Knockout Code (C): 1/2, 3/4, 1 In; Knockout Code (E): 3/4, 1-1/4, 1-1/2 In | Knockout Code (B): 1, 1-1/4, 1-1/2 In; Knockout Code (D): 3/4, 1, 1-1/4 In; Knockout Code (G): 1/2, 3/4, 1 InSouthern Tier Electric Supply