The difference in alcohol content.
Foreign screw caps are patented. Chinese breweries cannot infringe the patent, so they cannot use screw caps. Supplement: Literally speaking, "patent" refers to exclusive interests and rights. The word patent comes from the Latin word Litterae patentes, which means a public letter or public document. It was used by medieval monarchs to prove certain privileges, and later referred to the exclusive rights certificate signed by the British king himself. Patents are the world's largest source of technical information. According to empirical statistical analysis, patents contain 90%-95% of the world's scientific and technological information.