It's a steel rod with a hole for the bit. Sure, it does add reach to said bit, however a typical 1/8" sits loosely in the hole so that the two set screws that hold it in place actually offset it to one side, considerably reducing accuracy. On top of that those set screws actually stick out past the outer diameter of this extension making it impossible to use next to a wall of a part, for example. This would have worked far better if it was shrink-fit style holder. "Why did you not return it if you hate it so much?" By the time i was able to actually try it out the return date passed, simple as that.