No.20 standard glue No.20 standard glue is a kind of natural rubber, which is cut from rubber trees. Natural rubber can be divided into standard rubber (also called granular rubber), smoke film, concentrated rubber, white crepe film, light-colored film, transparent rubber and air-dried film. The most commonly used are standard rubber and smoke film. Standard glue is mainly divided into No.5 glue, 10 glue and No.20 glue. No.5 glue is the first-class glue and the best glue, with an impurity content of 0.05%; 10 glue is secondary glue, and the impurity content is 0. 10%. No.20 glue is a third-grade glue with an impurity content of 0.20%. Different kinds of glue have different uses: No.5 glue is generally used to make tire tubes; 10 glue and 20 glue are generally used to make tire casings.