The External item description allows a vendor or customer part number to be listed, however, it is a one to one relationship i.e. for one part, you can have only one vendors part number for a given vendor. In some industries such as automotive and electronic components, the same part number can have multiple references for the same part by vendor i.e. the vendor has a number part number every month which represent different internal build numbers however as essentially the same part. Furthermore, some external references are not tied to a particular vendor or group of vendors. For example, in automotive or electronic components, the part can be generically known by the manufacturers or OEM part number throughout the industry.