uses a ¼ dowel rod at .70 inches or 17.9mm for the normal file

file with .32 at the end uses a .32 inches axle rod or 8/25 rod at the same length of .70 inches

added new models that have a better response pattern to increase responsiveness. 

(Note: new response has only been tested on the mini butterfly model that l have and it seems to work quite well but l haven't been able to test the new response on any normal size throws yet)