I have a cp on my nikkor f/1.8 50mm and it works great, problem is I can't get it off. I must have stripped the thread maybe? I've taken it off pleanty of times so I now how to take it off since the filter free floats but I can't get the ring to budge at all. I even tried using my leather man and holding onto the grips but nothing. Anyone have any ideas? I really don't want to buy another.