Originally Posted by IBLUBYU
EDIT: I feel these lenses "degrade and crack" because when changing a bulb and re-installing the lense, the tendency is to tighten the screws too much.
Mine were not damaged at all because of overtightening, the actual material had broken down enough that they literally fell apart, and not just at the screw holes. Not to mention the plastic had yellowed/grayed and was VERY brittle, one more winter and they would fallen off the car....