H&R makes very good quality spacers. But the E39 is very sensitive to the use of these things on the front hubs. A 20mm spacer is a virtual guarantee of shimmy. And some E39s will shimmy with a 10mm spacer.
If you install spacers, you should get hubcentric ones that replicate the lip on the hub.
Left - 10mm spacer which replicates lip on hub. Right - H&R 5mm hubcentric spacer which doesn't replicate lip
A non-hubcentric spacer has a center opening which is larger than the lip on the hub. (For an E39, that is 74mm) Many of them are "universal" and have 10 slots and a large center opening so thay can fit on a wide variety of cars. Non-hubcentric spacers should be avoided at all costs.
The thinnest spacer available for the E39 which replicates the hub lip is 10mm and is not made by H&R. I don't recall the company that makes them, but these are sold by The Ultimate Garage.
Dave Z.