If ya absolutely gotta musta I can't stand it mama I just gotta have one, I would suggest the models with the flexible adjustment and variable speed.
Get the best one you can afford because when you ruin a good gun you will retire your dremel tool to polishing jobs and duck carving. Slow and easy is the way to go, file a bit, check the fit, file a bit, check the fit...
But then they are ok for bobbing a hammer spur.
Good Shooting
Red.
Ps..when ya get a new gun cause you ground the old one into powder...get a glock, you won't need any tools except a punch!