I sent a shadow slide to a reputable company ( no names at this point ) it came back with no pins and the mounting screws were over sized with the Vortex Viper's mounting holes drilled out for the larger screws. The mounting surface was not flat. I sent it back and they re-milled the surface flat. They stated the larger screws were needed to hold the viper in placed. At this point let me say this ... the pins hold the red dot from moving ... the mounting screws hold the red dot on the pins... I am highly upset over this. The dot failed within a couple hundred rounds... vortex did a warranty exchange. Now question Is ... do I weld the oversized holes up and start over and get the pins ... or just try to get pins and drill the new dot out... or drill the dot and run without pins. Oh and because the mounting holes are larger... I can not put the dot on something else and/or a different dot on the slide without drilling the holes out. I have a mess ... I could have done better than what I got on my buddies mill... but I decided to send it to a company with AAA+++ reputation thinking I would get a first class job and not have to worry about screwing it up myself.