Hey Everyone, I recently made an impulse buy as I thought it would be nice to have some added ventialtion for when Camping in my 84 Westfalia.  I bought two rear panel windows that contain the air vent at the rear of the windows.   I have a few questions maybe some of you can answer; Are there any known negative affects?   Water issues? Replacement filter type media on the exterior vent? Any special instructions for window guys putting them in?  Thanks Everyone,