Zircon 62349 StudSensor i20 OneStep Center-Finding Stud Finder with How-To DVD Find the center of wood or metal studs up to 3/4-Inch. (19-Millimeter) deep Zircon-exclusive SpotLite Pointing System clearly indicates the center of the stud ACT Auto Correcting Technology checks calibration 10 times per second and recalibrates automatically to ensure accuracy Includes Zircon How-to DVD and detailed instructions. Sensing depth and accuracy can vary due to moisture, content of materials, wall texture, and paint