These represent an important step forward in file technology. This multi-tooth tungsten carbide file will even cut case hardened edges (rock dings) and stay sharp. Line up file parallel with file guide for optimal performance. Carbide blades are 5/8 inch x 1/4 inch and are mounted on a new, improved aluminum backing plate. Single version has an Aluminum Oxide Stone for polishing edge after cutting. Pro version has two sets of cutting blades.