During the Middle Ages, the counts of Champagne owed their prosperity to the commercial exchanges. Along with the kings of France, they instituted the conduit des foires (network of fairs) that officialized the fairs of Champagne. Six major fairs took place throughout the region over the year, the most important in Troyes (Foire Chaude de la Saint-Jean and Foire Froide de la Saint-Remi). Money changers and bankers played a significant part, as only the coins of the counts and the king were allowed in the fairs. The Troy ounce, a unit of measurement for gold and jewelry, is still in use today in the Anglo-Saxon world.