I started out with one of the ones that looks like an L shape with a screwdriver on the long leg end. Perhaps this was an orriginal Colt design?? As it came it would not fit the small Remington recess but I got a friend to chuck it up in a lathe and give it a bit of relief. He did claim that the little tool was harder than a cheep file, which was what he used! Definitely would be a good way to lose a finger for the careless individual!!!