There's no such thing as 'OEM'.
Fake =/= OEM.
OEM means 'Original Equipment Manufacturer'.
Basically a company that manufactures components for other
companies.
For example, HP computers consist of parts from Asus, MSI, Delta
and Western Digital.
The latter four companies are called OEMs. They manufacture
equipment for use in another company's products.
For Beats, Monster Cable manufactures their own stuff and then
markets it. There is no background company doing manufacturing of
any sort for Monster Cable.
Therefore there is no such thing as 'OEM Beats'. They're
fakes.