Boxerworks.com

I am sure I asked about this before, but a search found nothing.
Motobins offer 2 rear main seals (same price).
The old style uses a garter spring, the new style does not.
Does anyone understand the pros/cons of each, and how to decide between them?

(After 120,000km I don't think the rms is leaking, but I would like to replace it while doing the clutch and switch to full synthetic oil.)

At that mileage I too would replace it. I do not replace good RM seals of much lower mileage. Sorry I can't offer up experience in those two seals. Someone will.

I have one of each in my two different /5 engines. Only 6000 miles on the new style and about 1500 on the old style.

No leaks. The new style is PFTE coated and does not need to be oiled on instalation.