Product Name: Precision Granite Square Ruler Model NO.: 400*400mm Material: Jinan Black Granite Grade: 00, 0, 1 Trademark: JINGDA Transport Package: Plywood Case Specification: see specific list Origin: CHINA Product Description It is precise in structure with black luster and through hundreds of millions years aging, It is of uniform texture, nice stableness, high intensity and rigidity, and can maintain a high precision under heavy weight. So granite is applicable to the works of industrial production and laboratory measurement.Type (mm)Squareness betweenadjacent measuring surfacesStraightness of measuringsurfaceParallelism betweenOpposite measuring surfacesPrecision grade (μm)000000000160 × 160240.81.724200 × 200240.91.824250 × 2502.24.5122.24.5300 × 3002.65.21.12.32.65.5400 × 400361.32.636500 × 5003.571.533.57If you are interested in our products, please contact us. All the standard size are in store and the special size can be made as your requirement, As a manufacturer, we can supply you very competitive price. Your enquiry is highly appreciated.