Rain-X can't be used on plexiglass or lexan glasses.

Read these threads, lots of info:

http://www.bikeforums.net/showthread...for-sunglasses
http://www.bikeforums.net/showthread...eir-sunglasses
http://www.bikeforums.net/showthread...in-and-glasses
http://www.bikeforums.net/showthread...rom-fogging-up
http://www.bikeforums.net/showthread...yewear-in-rain
http://www.bikeforums.net/showthread...in-Rain-Thread
http://www.bikeforums.net/showthread...e-rain-Glasses
http://www.bikeforums.net/showthread...nglasses-clean
http://www.bikeforums.net/showthread...in-and-glasses