Now that I think about it, I agree with lardy. The static cling ones would be better (on the inside of the window). That would save them from damage due to tampering, or even worse....scraping the ice off of the windows in the winter Plus you can move them around the car if you so please
Go for the static cling ones!!!!!

Jonnie

98 Zetec Contour SE Sony XPlod CDX-CA900X HU Sony XPlod XM-2150GSX amp with JBL 8" Sub (Not much so far but workin' on it)