FROM THE MANUFACTURER:

IRWIN® Impact Performance Series™ fastener drive bits are engineered for maximum durability and long life with impact drivers.  These power bits are designed with precision tip geometry  so they fit fasteners more precisely, which reduces stripping and cam-out.  Manufactured with heavy-duty, cold-forged, high-grade steel, they'll withstand extremely high torque output, and the black oxide finish resists corrosion and increases the life of the bit. They're designed with a 1/4" quick-change shank, so they work with all types of impact and rotary drivers.  Plus, they also have a unique Power Groove design for use with the exclusive IRWIN Magnetic Collar Attachment, which prevents fasteners from slipping and wobbling.