SPI Steel Rectangular Gage Block Set 81 piece set - Economy Grade Accuracy approximately + .00005" Certificate of Calibration included Included in this set... 9 Blocks 0.1001" thru 0.1009" in 0.0001" steps 49 Blocks 0.101" thru 0.149" in 0.001" steps 19 Blocks 0.050" thru 0.950" in 0.050" steps 4 Blocks 1.000" thru 4.000" in 1.000" steps