Detects wood/metal studs up to 19mm3 stage LED detectionAudio/Visual live AC detection alertHigh-impact, ergonomically-designed ABS case includes pencil notch for pinpoint marking Requires 9-volt battery (not included) The Stanley Stud Sensor/Finder 100 is a pocket-sized stud sensor that detects and locates studs and joists up to a 19mm depth. It is easy to use, with an audio and visual live AC detection alert and comes with a high impact case for safe storage.