This classification system tabulates the properties of thermoplastic elastomers (TPEs) that are intended for, but not limited to, use in automotive applications. For the purposes of this document a TPE is defined as a polymeric material that, without further chemical modification, is capable of recovering from deformations quickly and forcibly and is also capable of being repeatedly softened by heating and hardened by cooling within a temperature range characteristic of the material. When the TPE product is to be used for purposed where the requirements are too specific to be completely prescribed by this classification system, it is necessary for the plurchaser to consult the supplier in advance to establish the apropriate propeties, test methods, and specification test limits. This classification system is based on the premise that the properties of TPEs can be arranged into characteristic material designations. These designations are determined by type, based on resistance to heat aging; and class, based on resistance to volume change resulting from oil immersion. Basic levels are thus established which, together with values describing additional requirements, permit complete description of the propeties of all TPEs. In all cases where provisions of this classificaiton system would conflict with those of the detailed specifications for a particular product, the latter shall take precedence. this classificaiton is based on SI units.