The Society of Plastics Industry (SPI) has developed a code for the type of plastic used in plastic products. It is in the middle of a triangle consisting of three arrows, plus a number sign. On plastic products, the numbers 1 to 7 and English abbreviations are used to refer to the types of resins used in plastics. In this way, the identification of plastic varieties becomes simple and easy, and the cost of recycling has been greatly reduced. This SPI identification scheme has been adopted in many countries in the world today. China developed almost the same marking standards in 1996.