I have the OL-5519 and love it. HHA makes a great one pin sight. You'll love it!I have been using it for 3 years now, one of the best sights I've ever had in over 30 years. I even added a light kit 3 years ago to it and have never neeeded to turn it on. The only mistake I made with it is I should have got the OL5519. The smaller pin is better for longer distance.