Small mass realization in the new SI

On November 16 2018, about 60 countries met in Versailles, France and voted to redefine the System of Units (SI) based on seven defining reference constants. Since May 20 2019, the unit of mass is realized based on three fundamental reference constants: the Planck constant h, the speed of light c, and the unperturbed ground state hyperfine transition frequency of the cesium 133 atom Δν
_Cs
. With this new definition of the unit of mass, scientists at the National Institute of Standards and Technology (NIST) realized masses in the range of 0.05 kg to 0.20 kg directly on the NIST primary realization, and compared the results to the traditional work-down. This abstract shows the advantage and the improvement in the measurement uncertainty of mass in the small range that was only possible after the redefinition.