Answer
Car One-Way Vision film goes on the
outside of the rear window.
The see-through effect works by the dark backside of the graphic being attached to the glass with adhesive, so that it is taut and firmly-fastened to the glass. If you were to position the rear window graphic on the inside facing out, the graphics would not be visible due to the tinting that is standard on vehicle rear windows.
Car One-Way Vision is designed for outside vehicle use and is designed to withstand weather conditions and car washes.