I had the inside of my doors apart today to work on regulators and clips and it seems to me that the triangular plastic piece I ordered is what holds the window in. I can see a rubber seal on the interior (which is thankfully intact on my car) and I think that the pieces I ordered sandwich the glass in on the exterior. More to follow.

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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