Campy used to advertize grade 25 bearings at the same time I bought some grade 24 balls at a local bearing house in the united states at around 5 cents each. Bearing manufactures are constantly making small improvements they don't advertize. There used to be an exhibit in the Chicago museum that bounced ball bearings off two inclined planes to show how accurately they were made. Ceramic ball makers advertize they can be used without lubrication this is nice if you don't like to tear down hubs.