The sealed ball bearings are used as a means to limit the amount of friction that occurs between a fixed part of the assembly and a rotating shaft. They can be used for numerous applications in lawn and garden equipment. The ball bearings are used in various locations of different types of machines, so the issues that could crop up will vary. Typically, bad ball bearings will create knocking sounds in the engine, or parts in the engine could be difficult to turn. When the ball bearings are no longer sealed or not functioning properly, they should be replaced. This genuine OEM replacement ball bearing is sold individually. The ball bearing works with many models of lawn mowers, snowblowers, edgers, wood chippers, and tillers. Compatible brands include Craftsman, Toro, Cub Cadet, Ryobi, Troy-Bilt, Murray, Yard Machines, MTD, Huskee, Montgomery Wards, Bolens, Yard-Man, Turf King, and MasterCut. Buyers should always ensure they are buying the correct parts for their make and model.