This is a genuine OEM replacement part, it is sold individually. The purpose of the 738-04124A Shear Pin is to protect your snowblower. If the auger gets jammed or clogged, the Shear Pin is designed to snap at a certain point of pressure, so it will not damage any other part of the unit.
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.