Powders of vegetable and animal drugs are officially defined as follows Very coarse(No 8): All particles pass through a No 8 sieve(2.36 mm) and not more than 20% through a No. 60 sieve (250m) Coarse(No 20): All particles pass through a No 20 sieve( 850 um)and not more than 40% through a No 60 sievePowders of vegetable and animal drugs are officially defined as follows: - Very coarse (No. 8): All particles pass through a No. 8 sieve (2.36 mm) and not more than 20% through a No. 60 sieve (250 m). - Coarse (No. 20): All particles pass through a No. 20 sieve (850 m) and not more than 40% through a No. 60 sieve