What has me confused is it is unclear if the tip size to order is associated with bullet size or barrel size. Clearly a 50 cal tip won't likely fit in a 45 barrel, but the tips vary by bullet style causing me to believe the interior contour of the 50 MZ tip will be different than the 45 MZ tip. I've gone ahead with ordering a 50 tip. Just wish I knew if it will align a .40 bullet.