About a year ago I tried a comma as a side wheel for my Nikko Diamond 10-50. It was a Mac1 design http://mac1airgunstore.com/product_...d=369&osCsid=56741e3ada027282da344228d4f441f9 It's 4", so at the longer distances, from 45-55, it gives an effective wheel size of 8", but it's still able to fit in most rifle cases. Setting it up required aiming at an FT target at EVERY yard, from 10 to 55, as the spacing isn't linear. BUT from the 50 to 55 yard markings, I have a very clear distinction, and am able to always range find to within 1 yard. It works very well for me. I'm wondering why they're not more popular? Is it because of their requirement to setup every yard? Or am I missing some negative to this setup?