Pro35, stud sensor, stud scan mode locates edges of wood & metal studs up to 3/4" 19 mm deep, ready light indicates when calibration is complete & tool is ready for use, edge arrow lights up sequentially as tool approaches stud & fully illuminates when stud edge is located, zircon s patented over stud feature alerts if scan begins over stud, wire warning detection indicates presence of live, unshielded ac electrical wiring up to 2" 50 mm deep, spotlight pointer shines an arrow shaped image on scanned surface to clearly indicate edge of stud, "v" marker groove enables accurate marking of stud edge location, ergonomic grip for secure hold in either hand at any angle, uses 9v battery, not included.