Johnson Combination Squares are Built Jobsite Tough, with steel blades protected by anti-rust coating and permanently stamped graduations as small as 1/32 of an inch. Johnson Level offers 6” combination squares, 12” combination squares, and 16” combination squares (perfect for measuring distance between studs), with a variety of head materials including cast iron, heavy duty cast zinc, and Structo-Cast molded impact foam. All Johnson Level combination squares comes with durable acrylic level vials, and most models come with a built in scriber that screws in, so it won’t fall out.