Description:  Machinist Precision Edge Square Ruler 90º Right Angle Engineer Ruler Measuring Tool.     Specification:  Material: Stainless steel.  Size: 63x40mm, 80x50mm, 100x63mm, 125x80mm.  (2.48x1.57", 3.15x1.97", 3.94x2.48", 4.92x3.15").  Edge angle: 30°.  Seat Width: 5mm.  Accuracy: Grade 1.  Tolerance 0.02-0.05 mm.  Use For: 90° right angle measuring, designed for precision layout and measurement work.     Features:  1. For checking the squareness of an edge, using the light-gap method. The blade is bevelled on both sides.  2. Accuracy grade 1, squareness tolerance of 0.02-0.05 mm.  3. Supplied in a protective case.  4. Beams and blades are ground and lapped for parallelism.  5. 30° edge, beams and blades are ground and lapped.     Package Included:  1 x Edge Square Ruler