Apparently, the folks in France have to make a "new" kilogram.
Every metric measurement has been redefined over the years in terms of some constant physical property of the universe except for the kilogram. The kilogram is still the same old lump of metal (or clay or whatever it was) that has been sitting in that museum for over a century. Well, over time, it has eroded. THE kilogram (against which all other kilograms are measured) has lost 50 micrograms over the last century. So they are making a pair of new kilograms to last forever. (The second is a backup.)
I thought that 1 l of pure water was supposed to have mass of 1 kg (to be precise, weight is measured in newtons, not kilograms)? And that 1 l of water has volume of 1000 cm^3?