Prizms for viewing stoplights

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

JimSig

 

these things are great to hang your sun glasses on

 

Mine is glass 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.