I had to start over several times because if I aligned the sensor well, he has not aligned with the bottom of the phone (I started the first camera and sensors to be sure they do would not be covered). Repeating several times gave more chances for dust to get in and I had to use tape to clean it. I applied the protectors in the bathroom after taking a hot shower to enjoy the steam, and always had difficulties. The cuts are not very accurate. Once I finally got to put in place, it was perfect and as if she were not even there.
(Sorry for my French, I'm English)