They were fairly easy to install but I'm taking a star off them for two reasons: 1. One of them arrived with a broken locking clip that came loose had and got stuck in the outlet. I managed to get it out but this shows the level of quality control they use2. After installation, a significant amount of force is required to close the window. As previously mentioned, applying equal pressure to both ends of the lens will minimize the damage that can be caused if all of the pressure is applied at one point along the edge of the lens. In any case, I have to get involved.