The  12mm (1/2\") drill out is a revolutionary new tool that simplifies the often awkward task of removing broken bolts and studs. Used in a 3/8\" reversible variable speed drill, the left hand self-centring drill cuts down into the damaged bolt, then the tapered collet bites into the drilled hole and unscrews it all in one quick operation. Made from precision ground high speed steel. Works every time. See the How Do I Remove Broken Studs ? article in the Technical Articles section