I have used the Carey Side Sighter for several years, but I would like to know more about the mirrors. I believe Don Carey (carey enterprises) works out of Idaho in the summer and Arizona in the winter. Use google or trapshooters.com to locate him. Jack, the "one range convergence" is solved by not converging the sighter and the rib at one range, but by adjusting the sighter exactly parallel with the rib, which results in a pattern that is about two inches right of center, no big problem in the world of shotgun shooting.