This is durometer which was developed to comply with JIS K 6253 (new JIS) ruled in 1993 to confirm ISO ( International Organization of Standard ). It consists of 3 types of durometer such as Type A for medium stiffness, Type D for high hardness and Type D for low hardness.
Type A which is main type tends to indicate higher figure by 1 or 2 points compared with conventional A hardness measurement. Type D is suitable for hard rubber of which measured figure by Type A 90 and above and Type E is suitable for soft rubber of which measured figure is below 20.