The 77mm by 55mm Seismic Speed Vent is molded around our proprietary weight-saving Energy Conversion (EC) hub the first tall, wide hub seen in longboarding and still second-to-none. The 77mm diameter gives it the roll speed of a downhill wheel, 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. Poured in Seismics Premium Clear formula: the best beautiful clear urethane on the market smooth, fast, and grippy Features: 77mm tall x 55mm wide SPEED VENT Wheels 54mm running surface Offset bearing seat Square outside edge, beveled inside edge 7.1 oz. each Sold in sets of FOUR wheels