I broke the tab off the end of the enclosure on the old enclosure on my '06 LaCrosse (the tab circled in the picture) It's the one the metal collar goes on. I bought a new enclosure got it and tried to install it this afternoon. Same problem. I couldn't get that tab far enough toward the back to put the black collar back on. The inside side of the unit goes in perfectly. there is also a stabilizer tab that goes in a hole over where the arrow is pointing. That one is about an inch too short to be seated correctly. I can't find what is keeping it from going in right. If anyone has an idea on what my next move should be let me know. Oh, the picture isn't my car.