The General Tools MSV100 Stud, Metal and Voltage Detector can quickly and easily locate the edges and center of metal studs and joists behind walls, floors and ceilings. can locate wood studs/joists and metal cables/pipes behind walls or even inside furniture. It can also make the work of contractors, carpenters, plumbers, electricians and demolition crews safer by detecting energized AC outlets and "live" wires behind walls or ceilings. This detector automatically compensates for wall thickness. In voltage mode, it also automatically compensates for distance to wire. Center arrow and beeper pinpoint edges. A marking slot on top of unit makes marking precise and easy. A user manual and 9 Volt battery are included with every tool. SPECIFICATIONS Maximum wall thickness for wood detection: 3/4 in. (19mm)Maximum detection range for iron or copper pipe: 1. 5 in. (38mm)Maximum detection range for AC voltage: 2 in. (50mm)Operating temperature: 40° to 104°F (5° to 40°C)Weight: 7. 3 oz. (207g)Power source: "9V" battery (included).