headlight lens -- glass or plastic?

[CowboyBeebop]

On the bright side, it won't shatter like glass will. Do you even have to tape them up at the track?

Lighter and cheaper to replace aren't bad intrinsical attributes, either.

Are they in fact lighter?  I'd think they would be significantly.  If it is the case that they are lighter, I've got a glass lens in perfect condition that I'll trade for someone's plastic one.