61903 Pro SL-AC Stud Sensor, 1-1/2 in, Zircon International | StudSensor Pro SL-AC stud finder locates the edges of wood and metal studs and joists behind walls, floors and ceilings. Patented SpotLite pointing system shines a beam of light on the wall to identify the target and WireWarning detection indicates the presence of live AC voltage. Its tough, ergonomic housing withstands everyday jobsite use.