This part is listed by BMW as BMW part number 32416767244 (32-41-6-767-244) and is described as Genuine BMW Tandem Steering Pump (LuK LFR-440) for E60 545i, 550i (2004-2010) and E63/E64 645Ci, 650i (2004-2010).
For vehicles with Dynamic Drive and without Active Steering.
This is a Genuine BMW power steering pump with a two year warranty. Buying a Genuine part will usually be more expensive than an OEM or aftermarket brand but you are assured that it meets BMW's designs for fitment, performance, and longevity. It will also be the very latest design, incorporating any updates or revisions that an aftermarket brand typically will ignore.
BMW Fitments:
5 Series
E60 / E61 (04-10) > 545i
E60 / E61 (04-10) > 550i
6 Series
E63 / E64 (04-10) > 645Ci
E63 / E64 (04-10) > 650i