Fixion: Le Grand K

In a a maximum security vault at the International Bureau of Weights and Measures (BIPM), under the suburbs of Paris is a cylinder of platinum and iridium approximately the size of a raquetball. It is known as "Le Grand K" and the International Prototype; it is the only object known to man that has a mass of exactly 1kilogram. It is the reference from which the unit of mass is derived; every object measured in kilograms is defined by Le Grand K.