Just installed one on my K3. Worked like a charm. A very tiny bit big in the back though so I trim like 1mm off of it. The reason was because it was covering part of the page turn buttons on my side so I had to trim it to have it working properly. It might not bother other people but I am weird with stuff like that. Other than that it looks great and feels great. Now Britney (my K3) could really have a big come back.
Edit: I also have to peel it off a couple of time to line it up but it sticks back fine each time. So really easy to do.