The stud ball is a protected magnetic stud finder that will out perform any other type of magnetic stud finder on the market. Unlike other steel stud finders, the stud ball can detect metal through 1/2 in or 5/8 in drywall or other thicker building materials. Will also work through ceramic tiling and up to 3/4 in plywood paneling. Rare earth magnetic with 27 lb pull Detects screws or nails in wood frame walls No batteries required