you can double check winchester website for info maybe. my extrema 2 is backbored. with there recoil reduction pad shooting 3 1/2's isn't bad at all. I don't even know what constriction my choke is LOL, I heard a lot of good things from people regarding my choke and shot combo so I went for it last year and wasn't sorry. good point on missing em up close b/c of shotstring so tight. most of my shots are 18-50 yards. I don't worry about it much at those distances. I in know way represent nitro or rhino choke company's just as others believe in word of mouth when I come across a great product. my friend gets a pretty good pattern with the jelly head choke and winch supreme 6's. the nwtf is also a good site for info on choke, shot combo in there forums. just do a search.