FWIW, I believe these chokes are for backbored mobilechoke barrels. .730 bore diameter minus .025 points of constriction gives you .705 exit diameter. .735 bore diameter minus .040 points of constriction gives you .695 exit diameter. If used in a factory mobilechoke barrel at about .723 bore diameter, it leaves you with about .018 points and about .028 points respectively. YMMV... Somebody correct me if I'm wrong.