Do you know why there are only 21 stripes on beer bottle caps? Even the drinkers don’t know!

The 21-rib lid is strong enough to withstand the pressure of carbonation inside, while remaining simple enough to open easily with a bottle opener. The 21-pin lid is designed based on mechanical principles to provide a firm grip on the bottle lid. Initially, some lids were made with 24-rib lids, but these jammed in the automatic filling machines, disrupting production. As a result, the 21-line cover became the international standard.