Mainsail Country Codes to comply with World Sailing Racing Rules of Sailing.
Country Codes are sold individually for each side of the sail.
(a) National letters and sail numbers shall be in capital letters and Arabic numerals, clearly legible and of the same colour. Commercially available typefaces giving the same or better legibility than Helvetica are acceptable.
(b) The height of characters and space between adjoining characters on the same and opposite sides of the sail shall be related to the boat’s overall length as follows:
See the full document from World Sailing here: Racing Rules of Sailing 2021-2024