I see a few failure posts here for non-OE aux fans purchased off e-bay. A lot of the cheap/knockoff producers are producing molds directly off the OE/OEM parts, this makes their items look IDENTICAL to the OE/OEM items (even down to the BMW logo), while the electrical internals and materals are not designed/produced to the BMW OE standards.
Expect to do the job every year or 2 using the non-OE/OEM e-bay "specials", these are only "special" for owners/used car lots that want to get if fixed and sold.
I bought my '03 4.4 with a bad FSR, bought the E-bay "special", it failed in 6 mos, notified seller who replaced for no charge with another "special", it failed in 8 mos. Got an OEM FSR in place and had no problems for over 2 years. Having to do a repair 3 times and flushing the $50 spent on the knockoff part was not very special at all.
Helped a friend change out his upper rad hose assembly with an e-bay "special", where the OE unit had smooth tapered sealing areas in the plastic fitting, the e-bay "special" (with BMW logo) had mold mis-match and flashing on those sealing surfaces. He needed to use the truck and decided to go ahead with the install anyway. The assembly had the hose that goes to the alternator mis-clocked (pointed more foward) and about a 1/2" longer, he still insisted putting it in.
Once I wrestled it in the spring clips would not engage the slots in the mating fittings, had to put hose clamps around the spring clips to keep them from popping out! After getting everything buttoned up I hand spun the fan to find the mis-clocked/longer hose was sticking over 1/2" into the fan area. His X was laid up for 3 more day until an OEM hose assembly arrived, that went in with no issues.