Two kilograms which weigh the same (not a surprise) and have different buoyancy corrections.

These two kilograms were shown to me by Patrick Pinot at CNAM in Plaine Saint-Denis, France. On the left is one of the platinum-iridium kilograms assigned to France in 1889, K13 is "très" important, as quipped by fellow CNAM researcher Mark Plimmer. On the right is a stainless steel kilogram. The different sizes show the densities of the materials: steel compared to platinum-iridium, or ~8.03 g/cm3 compared to ~21.5 g/cm3.