I've always lived the cabrio A4 B6 and saw one with MOT for peanuts (£700) and snapped it up. I knew the drivers window wasn't working so today was job start day... I've removed the window and everything and put in the new stuff ready to go in the car, but a mystery but fell out when I was removing and I can't find any reference to it anywhere... Anyone know what this is and if I need it?!?