OK, got a third and fourth call from Stephanie at H&R regarding X5 spacers. Seems they're serious about getting to the bottom of the spacer part number discrepencies as we are. So here's the scoop for the 25mm (30 would be similar):

50757251, 50757252, 50757255
Let's break it apart- 50 75 725 X
50 means 50mm total width (2 spacers of 25mm each)
75 means a BMW with 5x120 bolt pattern
725 means 72.5mm center bore
Then the mysterious number on the end:
5 is a DRM spacer with studs to convert your X5 from bolts to studs and nuts.
1 is a DRA spacer which comes with 25mm bolts to attach the spacer to the hub.
2 is the same DRA spacer but with 30mm bolts to attach the spacer to the hub.

Seems the engineers in Germany thought of everything when designing the spacers and tried to build sets that tuners could use for their own needs, including big brake kits with thinner rotor hubs (25mm bolts) than stock rotors (30mm bolts).

FWIW- the 30mm spacers would then be 60757252.

Guess it's time to order up my 50757252 spacers.

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'04 E53, 4.4 Sport
'97 E39 528i
'86 911 Carrera, track car
'96 BMW R1100R