Set of 4 Ricta Speedrings Wide Skateboard Wheels in 54mm 99a. SpeedRings feature a specifically engineered core braced by two layers of urethane proven to maintain shape on impact. They also feature Ricta Rapido urethane, a balanced formula for maximum speed and smooth roll. Rapido urethane slides when you want it to and gives you control when you most need it. Long lasting urethane with fewer flat spots.