Country code in mainsail.
Well know are the three digit country code for in your mainsail. World Sailing and the Olympic Committee are using the three digit code as well. Not only that, according to the World Sailing rules, a thee digit code is mandatory for international events.
When purchasing a country code, you order one set. So you can place the country code on each side of the mainsail. For the best application of the country code, clean the surface first before adding the sticker on the mainsail.