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.