Three different synthetic rubbers had been mixed with natural rubber for the outside top sheet. Each three kinds have individual characteristics for :
Speed, Spin and Durability that is the basic technology for Yasaka's new concept "Energy Fusion Rubber". The sponge fusion also contains a certain level of synthetic rubber, which support a good speed glue effect. Sponge hardness: 38 degrees. Available in MX thickness only, for maximum power.