Calculated Industries 8110 Center Mark Drywall Recessed Lighting Cutout Locator Tool Perfect drywall recessed light fixture cutouts in half the time with NO measuring using powerful rare-earth magnets Twice as easy and only half the lifting of other marking methods Get professional results you can be proud of your first and every time with foolproof patented technology Pays for itself by avoiding costly and embarrassing measuring errors Fits 4", 5", 6" recessed (Non-LED) can light fixtures. Two included Targets screw into bulb sockets.