Beginning January 1, 2020, Class F calibration weights will no longer be sold for legal metrology use. According to the newly updated NIST Handbook 105-1 (2019), new weights for use as field standards placed into service for weights and measures use after this date must comply with all of the requirements of NIST Handbook 105-1 (2019).
However, existing NIST Class F calibration weights in the field will be considered grandfathered in and may continue to be used for legal metrology use as long as they meet NIST Handbook 105-1 (1990) requirements.
Although the new revision does supersede the 1990 version, it makes clear that existing Class F weights may continue to be used.
This change is taking place to accommodate for the increasing accuracy of weighing devices used for legal metrology. Class F weights are no longer sufficient for the calibration, inspection, or sealing of weighing devices used for the jewelry, cannabis and pharmaceutical industries.
Existing NIST Class F calibration weights may be reclassified to one of the new specifications if all specifications and tolerances fully comply with the alternative standard.
However, the NIST Office of Weights and Measures strongly recommends that you do not reclassify existing Class F weights due to the difficulty of performing compliance evaluation.
We are in the process of updating our weight descriptions on the website. So the item may say NIST F, but the weight you get will not be that. We ship 99.99% of our test weights direct from the manufacturer, so you can rest assured that you are getting the best and most accurate weight possible.