Irwin 6041706CD Strait-Line 150 Wood Stud Sensor with Built-in Tape Measure Accuscan technology is specifically calibrated for finding studs behind drywall, paneling or tile up to 1-1/2" in depth. Auto marking, no need for pencils and it keeps the surface clean. Automatic on/off with surface contact. LED and audio alerts clearly identify stud location. Built in tape measure allows for easy measurement from stud point.