Ryobi ES5500 Phone Works Stud Sensor Uses smartphone controlled calibration to locate studs under drywall up to 3/4 in. thick Accurately calculates center stud within 1/8 in. Features a built-in, one-handed stud marker for no-mess stud marking Shows live tracking of stud location from your smartphone screen Optimized for iPhone (OS 6.0 or later) and most Android phones (version 4.0 or later)