This 6306-2RS ball bearing is a high-precision premium quality sealed deep groove 30x72x19 ball bearing made to ABEC 3 precision standards from AXIS. What sets this 6306-2RS bearing apart from others is the ABEC 3 precision standard that this bearing is made to, the grade 10-balls used, and the superb electric motor quality rating (EMQ). ABEC 3 means that the bearing itself has a micron deviation from a nominal of 20.000mm of -8 micrometers. The standard ABEC 1 precision standard that almost all ball bearings are made to today has a deviation of -10 micrometers. In simple terms, the more precision a bearing is, the better it will perform in any given application. The grade 10 balls within this bearing are typically only found within ABEC 5 or higher bearings because of their more true roundness and precision. The balls within a bearing share the load capacity, so this also increases the working life versus the standard grade 25 balls used in other brands. The electric motor quality rating means that the bearing must operate at an extremely low noise level with minimal to no vibration. To achieve this, the 6306-2RS bearing features raceways that are precision honed to a superb finish.