Octagon box 4 inch diameter x 1-1/2 inch deep, has two 1/2 inch and two 3/4 inch side knockouts. Bottom has two 1/2 inch and two 3/4 inch Knockouts with a bump bottom ground hole. The box is used to install static ceiling or wall fixtures. With proper fitting can be used for conduit, NMSC, armored, metal clad, flex cable. The maximum support load for a static fixture is 50 lbs. Two 1/2" and two 3/4" side knockouts1-1/2 in. DeepDrawn with Conduit KO's, Raised GroundRACO® Octagon Boxes are used in the installation of ceiling or wall lighting fixturesAcceptable for use in 2 hour rated walls and ceilings15.5 cubic inches