DONIC Bluestorm Z1: A LIGHTNING STRIKE Z1 with its medium pored sponge and a short, wide pimple structure is the hardest and fastest of the three Bluestorm versions. It has immense power. However, in order to engage with so much horse power competent driver is required behind the wheel. A well trained player, master of the fastest game, will find Z1 to be a lethal weapon. Topspins with this rubber are quick as lightning!