4 LEDs display stud finder Stud Finder and AC Wire Warning with Four LEDsFeatures: 1) Detects 90 - 250V at 50 - 60Hz within 6" (150mm) of a hot unshielded wire 2) Detects wood up to 3/4" (18mm) 3) Auto calibration stud detection 4) 4 LEDs visual and audio indicators 5) Operated by one 9V battery (battery not included) Stud Finder and AC Wire Warning with Four LEDs