Class X grade pins with a starting diameter tolerance of .00004″ or .001mm and roundness limt of .00002″ or .0005mm ( note tolerance limits increase above .8250″ or 21.01mm per gage makers tolerance chart ). Used as masters to calibrate measuring equipment and check linearity of comparators, micrometers, and calipers. These “Tenth Step” pin gage sets have unlimited applications, such as quality control inspection, prototype work and production layout. Inspectors select from the range of pins to find the size of a hole or slot. These round masters simulate a cylindrical part which, unlike flat blocks, can detect uneven wear on the tips of micrometers and calipers. The thin “line” of contact detects uneven face wear better than flat gage blocks with large contact area.