With a HART stud finder, you have the fastest, easiest, most accurate stud finder on the market. There is no calibration procedure. You can instantly find studs. Once you have it on the wall, the precision LED display shows you right where the stud is. HART stud finders are the most accurate stud finders because they have more sensors. The HART Advanced has 7 sensors, so you can find stud positions with unbeatable accuracy. The display allows you to see the full width of objects such as single studs, wires, and pipes. The assembled product weighs 0.36 lbs. AAA Battery Powered: requires two AAA batteries (not included). HART Advanced Whole Stud Detector Stud Finder with 7 Sensors, AAA Battery Powered, Not Included.