This Standard Practice deals with the application of the International System of units (abbreviated SI) or SI metric units within the field of pulp, paper, and paperboard. TAPPI regulations require the use of the SI units as the preferred units in TAPPI Test Methods and other TAPPI publications Details of the SI are given in the various parts of ISO Standard 31: 1981 and ISO Standard 1000: 1981. Application of this information is not always easy, however. For instance some quantities can be expressed in different units, all within the SI. Such variations can lead to confusion in reporting test results and quoting property values. In order to overcome such problems within the pulp, paper, and paperboard field, ISO/TC6 has recommended appropriate units in ISO Standard 5651: 1989 (E). These are reproduced in this Standard Practice, together with other information and recommendations.