Update - My two triangular plastic pieces for the rear (small triangular) windows came in. They look to be the right parts as they have a rubber seal molded into the plastic that, I presume, seal the small windows. They look like they clip into the door frame with some push type clips, also molded into the parts.

Unfortunately I think I'll need to pull the glass out as it seems to sit inside of the part and the rubber seal. The rubber part is what has deteriorated and cracked off around the glass. I'm surprised I haven't seen leaks in the car. Of course it could be leaking down into the door cavity.

This will need to wait until I have some time. Hopefully later this month. Today I've got a few hours and am going to add some parts to my 4.6 motor, specifically knock sensors and the the valley coolant plumbing/rear coolant manifold.

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Current
Original owner 2002 E53 X5 4.4i to 4.6i swap
2026 G80 M3 6 spd
2025 G06 X5 50e
Former
1972 Audi Fox
1986 Saab 900S
1996 BMW Z3
1998 BMW E36 M3 Sedan
2004 BMW E46 M3
2006 Audi A3 Quatro
1993 Mopar 318 Jeep Grand Cherokee
2015 V6 Jeep Grand Cherokee