The flexible file is made of cast aluminum and plated steel construction, which is strong and durable and can be used to grind flat, convex or concave surfaces.The metal file designed with double-sided carbon steel has even teeth and is sharply and can sharpen edges quickly; no oil is required, just dry grinding or water grinding.The carbon steel files can be used for lead, solder and various types of car body fillers, such as filing metal sheets, steel, bronze, non-ferrous metals and plastics, etc., to achieve a flat, smooth and mark-free surface.