Section 1065.790 - Mass standards(a)PM balance calibration weights. Use PM balance calibration weights that are certified as NIST-traceable within ±0.1% uncertainty. Make sure your highest calibration weight has no more than ten times the mass of an unused PM-sample medium.(b)Dynamometer, fuel mass scale, and DEF mass scale calibration weights. Use dynamometer and mass scale calibration weights that are certified as NIST-traceable within ±0.1% uncertainty. 88 FR 4687 , Jan. 24, 2023 86 FR 34574 , 7/29/2021; 88 FR 4687 , 3/27/2023