1.1 This specification covers weights and mass standards used in laboratories, specifically classes 000, 00, 0, 1, 2, 3, 4, 5, 6 and 7. This specification replaces National Bureau of Standards Circular 547, Section 1, which is out of print.

1.2 This specification contains the principal physical characteristics and metrological requirements for weights that are used.

1.3 Maximum Permissible Errors (formerly tolerances) and design restrictions for each class are described in order that both individual weights or sets of weights can be chosen for appropriate applications.

1.4 The values stated in SI units are to be regarded as standard.

1.5 Weight manufacturers must be able to provide evidence that all new weights comply with specifications in this standard (e.g., material, density, magnetism, surface finish, mass values, uncertainties). Statements of compliance by calibration laboratories during subsequent calibrations must meet the requirements of ISO/IEC 17025, 5.10.4.2 and indicate on the calibration report which sections have or have not been assessed.