it's a little jig with a dedicated drill bit for creating HPs in loaded rounds. Works well for small runs, say for hunting or perhaps SD. I had one before I ever bought an HP mould and it worked fine for rifle and pistol. Get the larger version if you get one (1/8" bit), more versatile. Can be used in the Forster trimmer or you can just use a drill press (my way) or even a hand drill.