The Starrett CROBLOX S2CS 112.MA1 Square METRIC Gage Block Set contains 112 Blocks featuring 2 blocks .5 and 1.0mm-Steel, 1 block 2.0005mm, 9 blocks 2.001mm through 2.009mm (Steps of .001mm), 49 blocks 2.01mm through 2.49mm (Steps of .01mm), 18 blocks 1.5mm through 10.0mm (Steps of .5mm), 29 blocks 10.5mm through 24.5mm (Steps of .5mm)-Steel and 4 blocks 25mm through 100mm (Steps of 25mm)-Steel. This set has a B89.1.9 0 Accuracy Grade and features a combination of both 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. As well as traditional high-grade Steel, which are generally used in shop floor environments. An ideal combination of value, price and convenience, these sets include a popular selection of croblox (chromium carbide) and steel.