Powdered Sugar Confusion

What does "10X" and "4X" written on boxes of powdered sugar mean?

--Brenda

Powdered sugar (also called confectioner's sugar and icing sugar) is granulated sugar that has been ground to a fine powder.  A small amount (usually about 3 percent) of cornstarch is usually added to prevent clumping.  The "X" designation refers to the fineness of the particles, with 10X being the finest, and 4X being the coarsest.  They can be used interchangeably.

--JP