This is where it all began, 30 years ago - Polisport started building aftermarket parts so that everyone could enjoy their bikes without worry and with even better looks and improved performance. Performance plastics kick-started its success and are still the core of Polisport. Durable polyurethane with mechanical seals pressed over bearings that extend life. Will last much longer than expensive O.E.M. rollers. Stronger than stock rollers.