window tint ?

[adder]

i have a 98 firebird and the tint on the passenger door is coming off, it seems to be coming off in a line where the window runs down, i know i have to take the door off to find whats causing it before i go ahead and replace the tint but my question is the window has ez-kool marked on it i think that is the window itself as its raised to the touch i was hoping to find out so i only have to replace one window tint but im not sure of the grade so i guess i have to re tint both windows

any help would be great if you have a 98 firebird or camaro and it also says ez kool on the glass so at least i know where to start

best wishes

Adam