Made from Special Quality Steel, Hardened & Ground to 55 to 60 HRC, Ground and finished on four sides, Precision Ground in matched pairs, Variation in matched parallels is within 0.010 mm, Thickness, width and length are nominal and within ±0.1 mm upto 200 mm Length , ±0.2 mm upto 450 mm Length. Accuracy for Parallelism & Squareness is ±00005 mm upto 200 mm Length and ±0.010 mm upto 450 mm Length. All the four sides are chamfered. As per IS 4241-1967.