The glass is a little less than 1/4" thick and has only a very small area for the projector beam to pass through without fluting. The rest of the lens with fluting in addition to the refraction of the glass reduce the light output onto the road. Regardless, night visibility is drastically increased with a proper HID projector retrofit (my profile) even though dreams of crispy & aggressive cut off lines on other people's cars/surroundings will be shattered b/c of the glass lens.