The Sound Machine Middle pored sponge, new lighter sponge technology. 42.5° sponge, Bluestorm`s softest variation. Bluestorm Big Slam, is the fifth version that completes the series. This version has the softest sponge at 42.5° and has a strong speed glued sound and feel. The extremely thin high tension top surface rubber, in combination with a new lighter sponge technology has resulted in a rubber with great feedback and performance.