Originally Posted by
Inertianinja
do you clean the windows before attaching it? my only reservation with these things is that dirt on my window could screw up the seal.
Yes, I make sure the window and the paint is clean before using them. The company actually recommends you clean the surface and wet the cups before installing to make a better seal. The orange painted on the plungers also makes it easy to see if they don't make a good seal (also it makes it easy to visually check them when you stop).