This document is the primary American National Standard for use of the International System of units (SI). It includes information on SI, a limited list of units recognized for use with SI, and a list of conversion factors, together with general guidance on style and usage. The scope from the previous PAR was as follows: "Prepare the primary standard on metric practice for use in the United States. The word "primary" implies that other metric standards in the U.S. should be consistent with this document."