This set consists of 30 comparison specimens, covering 6 commonly-used machining methods (6 turned, 6 end-milled, 6 horizontally milled, 6 surface-grinded, 3 lapped, 3 reamed/drilled. A label gives the Ra values of each specimen in both metric and imperial units. (Rz-value label available on request).

Nominal value of the specimens:
- Ra µm 0,05 - 0,1 - 0,2 for flat lapping and reaming
- Ra µm 0,4 - 0,8 - 1,6 for grinding
- Ra µm 0,4 - 0,8 - 1,6 - 3,2 - 6,3 - 12,5 for milling and turning