Often the data recovery is impossible without replacement of the faulty drive part. Sadly there is no way to buy the head assembly or the main SMD element separately, so we buy the hard drive we will use for parts. We call it "donor".
Unfortunately there is no way to have a full collection of parts: there are thousands of different data media models, types, modifications. It is the reason why data recovery professionals frequently make operations on exchange of parts, or purchase the parts on ebay or ali express.
We have huge parts amount which reached 30.000 items. Thus we can handle a rich diversity of data media for data recovery as we know we have parts fro most of them.