TRADE NAME and SI UNITS DISCLAIMER Certain commercial components used in the reference standard are identified in this document in o(der to adequately specify the design. Such use and identification does not imply recommendation or endorsement by NIST nor does it imply that the identified items are necessarily the best available for the purpose. The International System of Units (SI) is used except in the dimensioned part drawings found in Appendix B. The shop which made these parts was not equipped to use metric dimensions. Economic resources are not currently available to convert the drawings to SI units.