irish944turbo

Spot of bother here guys. Previous owner had to get the lock rekeyed, as he lost the keys. Tried to lock the glovebox last week and the whole cylinder and mechanism came out. Got it back in and it took ages to engage it and the tiny copper spring at the back to the dash. One problem though, it didn't have a sealing ring to keep the whole lock in so I ordered one through my OPC. Have the ring now but it's far to big a diameter by about 10mm, does Porsche expect you to cut this ring to size. Part no. is ordered was 944 538 529 00. Can someone help me, I surely thought that this part would be car specific and the correct size and that you just pop it around the lock cylinder. If anyone has a photo of their glove box lock from the front I'd appreciate it.

Thanks in advance
Gareth