Hello Chief; I was in the same boat you are in last summer. My wife got me a set for a birhtday present, the back sight comes with two apetures. My set had the wrong front sight,the holes lined up all right but the base was too long and hit the barrel band. Call them up,there great people to deal with. I told them what I had, a New Marlin 1894S w/20"barrel. They apologize and sent the right one out. I let they tell me what I needed and it works Great! By the way I have a Lyman peep on my Black Powder Rifle, it works good but its not a AO. For the extra money get the AO it will be cheaper in the long run. I hope I didn't get you more Confused. Have a Happy New Year!