The NIST Office of Weights and Measures proficiency testing program is limited in scope to only those calibration laboratories who participate in our U.S. Regional Measurement Assurance Program and conducts proficiency tests only in mass calibration, volume calibration and length (steel tapes and rules) calibration. (Ref. NISTIR 7214, sections 1.0 & 1.6.) In addition to the program publications posted below, you can read more about our program operations in this paper, which was published in the NCSL International, Metrologist, June 2012.