The Starrett CROBLOX S2C 77.MAA Square METRIC Gage Block Set contains 77 Blocks featuring 5 blocks .5mm, 1.0mm, 1.5mm, 2.0mm, 2.0005mm, 9 blocks 2.001mm through 2.009mm (Steps of .001mm), 50 blocks 2.01mm through 2.50mm (Steps of .01mm), 5 blocks 3.0mm, 3.5mm, 4.0mm, 4.5mm, 5.0mm, 5 blocks 10mm, 15mm, 20mm, 25mm, 30mm and 3 blocks 50mm, 75mm and 100mm. This set has a B89.1.9 00 Accuracy Grade. Constructed of Chromium Carbide blocks which is the superior gage block material. Making these gage blocks the most stable measuring devices ever developed. Considered to be the top of the line, finest available.