Quote:
ABC1234 or ABC1234-G
A part number shown like this denotes the part to be Genuine.
ABC1234-A
A part number shown like this denotes the part to be of high quality and most likely to be manufactured from the same factory as the genuine part, OEM.
ABC1234-B
A part with "-B" at the end is a copy. The quality of the "-B' parts can be poor. If buying electrical items or items like water pumps be careful. For example we rarely use "-B'" parts in our workshop. They are cheap but in some cases you get what you pay for. That said some times the "-B" parts are absolutely fine and can save you $.
So if an advert refers to replacement parts as "aftermarket" there is usually an understanding that they are cheap and possibly poor quality. Which is fine if you want to take a chance that the parts will be ok.