Promark Jim Wunderlich System Blue - S Marimba Mallets. The Jim Wunderlich Series marimba mallets feature a rubber-like synthetic core wrapped tightly with durable synthetic yarn on a lacquered birch shaft for a smooth finish with maximum strength. The vibe mallets feature a rubber-like synthetic core wrapped tightly with cord on a rattan shaft. While they have durable components for outdoor environments, the lush tone of these mallets is an appropriate and tasteful choice for indoor concert or marching settings.