MAXIMUM FIREPOWER! We tweaked our popular 170mm "+8" extension for 40 S&W, giving you a chance to load up to TEN additional rounds! That 25+1! We've also re-profiled the interior to better accommodate the new "chisel-point" followers. Details matter, so depending on which combination of mag tube/follower you're using, results vary between +9 and +10. This extension can be used on a 22-round magazine, but requires a special spring -- if you'd like to go that route, please say so when you order. Ships with a custom-made Wolff spring. Due to U.S. State Department restrictions, we cannot ship this part internationally.