In 2011, a resolution to consider the future revision of the definition of SI units was considered by the General Conference on Weights and Measures (CGPM) in Sèvres, France. It still required final approval, and implementation would not be before 2014. In the “New SI” an “explicit-constant” formulation would apply to four of the SI base units. Thus the kilogram, the ampere, the kelvin and the mole, would be redefined in terms of invariants of nature; the new definitions will be based on fixed numerical values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (k), and the Avogadro constant (NA), respectively. Most notably, for the first time, the kilogram would no longer be defined by the international protype, a specific metal object and its possible subtle variation in mass.«[Image right: The international protype kilogram, as kept in the Pavillon de Breteuil, Paris, has changed by 50-micrograms since 1889.]