Wheel bearings can need replaced for a number of reasons, the most common being normal wear. If the wheel turns with a gritty feel or there is a loud metal to metal noise while driving, it's likely that the bearing has failed. A simple way to check your bearing is to lift the wheel off the ground and try to move the tire back and forth, by pushing the top and bottom of the tire in. If there is play, this commonly means the wheel bearing has failed.
This wheel bearing includes the necessary installation hardware. Changing bearings in pair is always a good idea, when one side fails it's not uncommon for the other side to follow suit.
