Seismic Tantrum Wheels 68mm x 43mm 81A set of 4. 31mm running surface, Centerset bearing seat, Double-radius profile. The 68mm by 43mm Seismic Tantrum is molded around the special fin-trimmed version of our proprietary weight-saving Energy Conversion (EC) hub - the first tall, wide hub seen in longboarding and still second-to-none. The big, airy, fiber-reinforced hub combines with perfectly-refined proportions, superbly-supported radiused edges, and our advanced urethanes for a truly progressive freeride experience.