Seismic Speed Vent Wheels 85mm x 52mm 78.5A set of 4. Offset bearing seat, 50mm running surface, Radiused outside edge, square inside edge. The 85mm by 52mm Seismic Speed Vent is molded around our proprietary Energy Conversion (EC) hub - the first tall, wide hub seen in longboarding and still second-to-none. The 85mm tire provides downhill roll speed, while the weight-saving hub adds the quickness and agility of a smaller wheel, as well as enhanced rebound. Combined with lips designed for pure grip, the Speed Vent stands in a class by itself.