This hub fits SOME 09-11 RX8s. Some also use the 33-04X0-F151. If you have an 09-11, please look at your hubs. The difference between the F151 and the F189 is the electrical connector on the back. Look at the pictures here and on part 33-04X0-F151 to determine which hubs you have. 

This is the only way to do front wheel bearings on your RX8. The bearing is not available separately.