CTC black tea is categorized into various grades based on the size and quality of the tea granules. These grades range from fine to coarse.
The different grades are
BOP (Broken Orange Pekoe): This is a much smaller grade than the leaf grades. It usually contains bud leaf, which is the mainstay of a blend.
BOPSM (Broken Orange Pekoe Souchong): This is a specific grade of Broken Orange Pekoe.
BP (Broken Pekoe): This is slightly larger than BOP, with somewhat less color. It is useful as filler in a blend.
OF (Orange Fannings): This is a CTC Fannings grade specially suited for tea bags throughout the world having very strong liquoring characteristics with bright infusions.
PD (Pekoe Dust): This grade is especially suited for tea bags having very thick strong gutty cups and bright infusions.
Dust: This is the smallest grade, useful for a quick-brewing, strong cup of tea. It is only used in blends of similar-size leaf, generally for catering purposes.