iPhone 4 Display Assembly Replacement
When I removed the screw from here I also found a small rubber piece. It is about 8mm long and 2mm wide, and it has a channel down the centre of it. I couldn't figure out where it came from but the phone seems to be perfectly fine without it. I thought it could possibly be some sort of anti-vibration damper for the vibrator although I am not sure. I couldn't see it in any of the pictures.