... requirement to manufacture it.7. Shield/closure: Open ball bearing, Z, ZZ, RS, 2RS, 2RZ 8. Internal clearance: C2, C3, C4 ,C5 ... BEARING DESIGN CLASSIFICATIONHasp type pressing steel cage. The most common type ... .With C2,CN,C3,C4 and C5 internal clearance.BEARING EXTERNAL DESIGNZZ 2RS double sealed design. Dust proof and leak proof grease ...