3-1/2 in round 1/2 in deep, old work Pan Boxes with (2) 1/2 in conduit knockouts are used to mount ceiling, and wall lighting fixtures when a shallow depth box is required. Their versatile combination head #8-32 screw can securely fasten fixtures to electrical junction boxes using a slotted, Phillips®, or Robertson head screw driver. This item has a 2 hr fire rating. GARVIN® Pan Box, Old-Work Cut-In, (2) Bottom Knockouts, (2) 1/2 in Bottom Knockout, 3-1/2 in Diameter, Round Shape, Steel, Zinc Plated, 1/2 in D Dimensions