Surface Plates-Black Granite *Granite Surface Plates meet or exceed Federal Specification GGG-PG463c. *Does not rust or corrode. *Does not nick or burr. *Harder than steel. *Retains accuracy for years. *Guaranteed repeat reading. *Auto-collimator checked for overall accuracy. For more details, please kindly visit our website. In addition, we also supply the following products: (1) Measuring Tools------Vernier Calipers, Electronic Digital Calipers, Micrometers, Dial Indicators, Squares, Protractors, Gages, etc (2) Machinery Accessories------Tool Post and Holder, Collects, Chucks, Drill Chucks, Milling Arbors, Sleeves, Vises, Working Tables, etc (3) Cutting Tools------including Drills, End Mills, Milling Cutters, Slitting Saws, Saw Blades, Reamers, Taps & Dies, Tool Bits, Carbide Inserts, etc (4) Machinery------Metal Working Machinery, Woodworking Machinery, Shear Bending and Rolling Machine, etc