"The S50 stud finder detects wood and metal studs up to three quarters of an inch below surface material and features auto-calibrating AC detection. With a sturdy design, this stud finder indicates when it senses a wood or metal stud below the wall surface with sequential LEDs marking both the edges and center of studs with accuracy up to 1/8" for wood and 1/4" for metal. Detects wood and metal studs up to 3/4 in. beneath surface material; stud center-find indicator for metal and wood; edge detection indicates both edges of the stud with accuracy up to 1/8" for wood and 1/4" for metal; visual LED indicators on face of stud sensor for easy readability; high impact, ergonomically designed ABS case"--AceHardware.com.