Grier CG 18A White A/O grain and CCG, the most popular mix is a friable very aggressive combination.
Grier CG 17A Gray A/O grain and CCG, a semi-friable mix that is less aggressive and therefore gives a longer life.
Grier CG 19A Pink A/O grain and CCG in combination that is popular for use with stainless steel, high nickel alloys and high carbon/high chrome materials.
Grier CG 16A Ruby A/O grain and CG in a rather new treated mix has been found to perform well with softer metals such as aluminum and brass.
When ordering, if a specific finish is desired, you may find that a finer grit size than you normally use is necessary because of the sharpness of CG.