You are confused about "OE" and "OEM"

The BMW part, with "BMW" on the box is OE.

The part as made by the manufacturer of the OE part is called the "OEM" part. I don't know who the OEM is for the compressor so I cannot tell you which is the OEM part.

"Rock Auto" is just a storefront- that part is a cheap, 3rd world knock off. There is utterly NO WAY I would was my time and freon on that. (Unless you are an AC tech with your own machines)

One of the things I don't like about rockauto (unlike say FCPEuro) is that they don't take the time to clarify OE/OEM/mfg info. Instead they seem to place a layer over this to obscure it. If they printed the Indian/Chinese/whatever name of the mfg for much of their parts, I wonder how that would go?

In terms of what parts you need to replace, what happened? If you have a leaking compressor versus a grenaded pump with metal distributed though the system.