Received this and went to mount on CVA Optima V2. Front site is straight forward. Rear site not so much. Durabright Quality Control dropped the ball. This set comes with a small allen wrench to loosen a screw which allows the rear site to be adjusted or taken off to access the hole where site is screwed to barrel. Well interesting that the screw in the side of mine was slotted for flathead, so I got a free worthless little allen head wrench. I figured no big deal just use the flat head. Wrong was not even tight and the the very shallow slot in the screw was already stripping. Very poor quality.