Every ball used in a FIFA or confederation match has to carry one of three quality marks, and the marks are not decorative. They are the outcome of seven laboratory tests with published numeric thresholds. Read those thresholds closely and the top mark turns out to allow a football exactly half the slack the middle mark allows.
The document that governs this is public and almost nobody reads it. FIFA’s Testing Manual for the FIFA Quality Programme for Footballs runs to 21 pages and sets out, test by test, what a ball has to survive before a manufacturer may print FIFA QUALITY PRO, FIFA QUALITY or FIFA BASIC on it. There is a machine that measures 4,500 points on the surface of a single ball. There is another that fires it at a steel plate 2,000 times. There is a tank that dunks it 250 times to see how much water it drinks.
