This is unmalted rye that has been de-husked, steamed, and then rolled between heated rollers to form flakes. The cooking and rolling process "gelatinizes" the starches, making them readily soluble and digestible by the enzymes in the mash. This allows the flakes to be added directly to the mash without any special treatment.
Flaked Rye gives a dry, crisp, strong rye flavor to most ales. Use 1-4 oz in light ales, 2-8 oz in darker ales.