Products     U.S. Domestic Standard   Cobalt % Grain Size For R-0 through R-10     GC-106 6 Fine GC-206 6 Medium GC-209 9 Medium GC-313 13 Medium For R-10 through R-19 GC-313 13 Medium GC-315 15 Medium GC-618 18 Medium/Coarse GC-970 17½ Coarse All pressed nibs meet or exceed the industry's highest precision standards: +0.000" to -0.003" (I.D. < 0.200") +0.000" to -0.005" (I.D. > 0.200") Tolerances for dies in sizes larger than R7 are determined by grade and inside diameter.