I have used them and had 4 or 5 around here for awhile, Personally I didn't like them, they seem to open up the accuracy of a rifle unless you fit the cocking piece then its tight and that bothered me..Most don't really hold a zero well IMO...I gave up on them and started using the Williams ghost peep that is a small affair on top of the rear ring, with nothing protruding off either side...Now if I can just talk someone into making the same in steel...

BTW, I sold all the cocking piece sights I had, so don't ask...