Prizms for viewing stoplights

Anybody know which ones are gl*** and which are plastic?
I've heard the gl*** ones are better, but I imagine finding one would be tough.

JimSig

 

these things are great to hang your sun gl***es on

 

Mine is gl*** and they're available from outfits that sell restoration stuff. Chevrolet's of the Forties and Cantor's have them.

 

Speedway use to sell a real prizm style looked good not bulky IDK how well it worked but i see they discontinuned them.

 

Installed the light in sight, works great.Thanks for the help.