TSR(Technically Specified Rubber) or commonly known as block rubber in Thailand can be divided into three main standard types, STR10, STR20 and STR Compound. They are chiefly used in the production of tires. TSR are graded according to a variety of factors, including dirt content, ash content, volatile matter, color and viscosity or portion of chemical contents such as carbon black, steric acid, etc.

Each major producing country establishes its own TSR standard with regard to the international ISO standard, with STR (Standard Thai Rubber) being the symbol used in Thailand, SIR (Standard Indonesia Rubber),and SMR (Standard Malaysia Rubber) being the symbols used in Indonesia and Malaysia respectively.