The STANLEY FMHT77407 FatMax Stud Sensor 300 featuring a backlit LCD screen which clearly displays all of the sensor's readings, even in low light conditions. AC detection identifies live wires up to 2 deep, along with Wood & Metal stud detection through up to 1-1/2 deep surface material. Also features a deep metal scan what sense metal through up to 3 of material. Its One Pass center-find technology is able to locate the stud center. This unit also features auto-calibration. The marking channel improves accuracy of marking-out readings. New ergonomic design, and soft grips provide comfort and control of the tool. Uses (1) 9v Battery, not included.