120 year old cylinder that defines the world standard for one kilogram to be replaced by sphere of silicon 28

The 120 year old International Prototype that defines the world's standard for the mass of one kilogram, held at the International Bureau of Weights and Measurement in Paris (BIPM), is set to be replaced by a perfect silicon crystal sphere developed by scientists at Australia's CSIRO. According to the CSIRO, the international scientific community, under the auspices of the BIPM, decided to focus on several methods for redefining the kilogram. One of those was the Avogadro Project that sought to bring together enough atoms of one substance to make the perfect kilogram. The sphere was made from one isotope: silicon 28.