Amylase enzyme is used during the mashing process when there are not enough naturally occuring enzymes, typically due to a mash containing a high level of adjuncts. Also used to more rapidly and completely convert starches into sugars. Usage varies, but the typical dosage rate is 1/4 oz per 5 gallons.
Comes in two sizes -- 0.25 oz and 1.5 oz. The 1.5 oz size comes in a resealable pouch, and can be stored for later use.