I dropped the tank to replace the fuel pump on my 2000 P38 (Only took 30 minutes to remove after the practice I had on my 95). When I went to reinstall the new fuel pump I found that the locking ring is too big to screw onto the threads of the tank. There's two options for the locking ring: the red plastic one for GEMS and the metal one for Bosch/Thor. I bought the metal ring (ESR3808) which is the same size as the old metal ring which came off.

I'm pretty confused at what could be wrong here. The old fuel pump appears to have some sort of collar (it ended up cracking when removing the old locking ring) which the new pump doesn't have. This collar is the perfect size and has threads to fit the metal locking ring. When I looked at pictures of WFX101100 and WFX101100 they don't appear to have this collar.

Old Pump With Collar:

Mysterious Plastic Collar:

New Fuel Pump:

Any ideas?

I found an picture of someone else changing the fuel pump which shows the ring around the tank that I'm looking for.

After a bit of searching I believe this is part number ESR3807. This isn't referenced in any P38 parts diagrams I've seen which is odd. The seal ring is ESR3806 and the locking ring is ESR3808 so it seems highly likely that this is the right part.