To install, I scored around the original lens cover with a needle to remove what appeared to be adhesive. A jeweler's loupe came in handy here. Eventually, I was able to pry the lens cover off (with the needle) in broken pieces. The lens cover is adhered to a rubber-like base (a lot of folks have noticed that the lens cover seems to float a bit when pressed) and I would recommend heating the area before trying to remove (I didn't). Once off, I installed the sapphire window (12.0mm x 1.0mm is a perfect fit) and applied pressure all around and it seems to have adhered to the rubber base OK. I've had it on for a couple of weeks with no problems. The only thing that is different (other than the extreme clarity and hardness) is the original had black paint on the back to decrease the aperture. This doesn't seem to cause any problems, but in some circumstances may cause some adverse effects. I haven't seen any yet, though.
Hope this answers your question..