This part is from original manufacturer. It is found in many models of Craftsman lawn tractor. This bearing fits between the rim and tire. A bearing secures a moving part for correct directional movement while allowing rotation. Because bearings are high-wear parts, it is not unusual to replace them often. This flange bearing is sold individually.
OEM stands for Original Equipment Manufacturer. Simply put, this means that the company who made your appliance is also supplying the replacement part for it.