Super tension back soft rubber. When its mark V and standard 10 speed 11 +. If spin 10 criteria and its mark V 12. If the control was standard 10 and its mark V 8. Rubber made of Yasaka STS (spin tension system) that their own production methods. It is selling a powerful spin speed and hitting sound is obtained without using glue-bouncing,. In addition to fast, spin is often take rubber.