A Factory Mercedes part would be an OE or original equipment part.

An after market part is a part that should fit but is a copy made by someone else for the car. These can be questionable quality.  Some are good but large amount of them are not.

An OEM part is an original equipment manufacture, meaning it is the same part made by the same company the same way with the same material as the factory specifies and is one of the companies that makes the part for Mercedes. Mercedes for many of their parts uses more than one OEM supplier for the same single part.

The main difference between an OE part and an OEM part is the price. Mercedes does not make most of their parts themself. They contract the part with their specific specs and design to other manufactures like Bosch, Behr, etc.

The part that is OE Mercedes is packaged in a Mercedes box or labled with the MB star.  The only difference between OE & OEM is Mercedes is not adding a profit for themselves to the OEM part.

OE part = Quality, Fit, Mercedes Box, HIGHER COST

OEM part = Quality, Fit, SAME AS OE, Manufacture package, LOWER COST

We carry some of all the above mentioned parts.

We carry an OE part in some cases because less costly OEM part that is the same item is not available.  These items are handled for our customers convience.  The price savings compared to Mercedes is not as high as an OEM part handled due to the added profit that Mercedes adds on to them.

Majority of our items are OEM with the highest savings to our customer for the item without compromising the quality.

Aftermarket items are handled but only when we are sure that the quality and price savings are worth it.

Many use the OE & OEM words with deception for the sale.  Be careful of words like OE quality, spec or equivelent along with many other trick in words that are purposely misleading.  I am sorry to say that many also outright lie with the OE or OEM claim.  You should always be aware that you are buying from a reputable seller with a good reputation with a good return policy if you are dissatified. Know what you are buying for part fit, life and most important your personal saftey. 

Thanks for reading

Rudy