DONIC Bluestorm Z3: A THUNDERBOLT Z3 with its large pored 42.5° sponge is considerably softer. This makes a big difference. One not only feels it but also hears it. Lovers of freshly glued rubbers will delight in the sound. An attacking stroke with Bluestorm Z3 sounds like the crash of thunder, yet the topspin player remains in full control. Feel the clap of thunder!