This is a remarkable stud sensor. Not only is it easy to use, but its readings are practically impossible to misinterpret. At 7" wide, it covers a broad test area, with sensors that independently scan up to 1 1/2" below the surface. As soon as any of the 13 sensors detects material of greater density than the surroundings, they display its position using 21 closely-spaced red LED bulbs, highlighting precisely where the obstruction lies.