Powder Fineness (Types of Powder) : Pharmaguideline
Superfine powder A powder of which not less than 90 percent by the number of the particles are less than 10 micron size. When the fineness of the powder is described by means of a number, it is intended that all the particles of the powder shall pass through a sieve of which the nominal mesh aperture, in /lill, is equal to that number.