Zircon StudSensor Pro SL quickly and easily locates the edges of wood and metal studs and joists behind walls, floors, and ceilings. The patented SpotLite Pointing System shines a beam of light on the wall to identify the target. Stud Scan mode locates the edges of wood or metal studs up to 3/4" (19 mm) deep; DeepScan mode doubles the scanning depth to 1-1/2" (38 mm); Red LEDs light up every time a stud edge is approached; Patented SpotLite Pointing System, an audio alert, and a green LED signals when the stud edge is reached; Should scanning begin over a stud, Zircon's patented "over-the-stud" indicator alerts the user to start the scan in a new location; Patented TruCal technology calibrates to any wall's density and a steady green LED TruCal light alerts the user when the tool is ready and calibrated. Clamshell package.