M2 high-speed steel cutting edge welded to a shatter-resistant spring steel back. SPEED SLOT features a staircase designfor easy plug removal. 4/6 Vari-Tooth design for aggressive cutting action and reduced vibration. 3/16" thick heavy-duty backing plate is more durable than stamped backing cups and eliminates need for torque driving plate. Use for heavy-duty cutting in stainless and mild steel, cast-iron, copper, brass, aluminum, plastics, wood, and composition board. Thanks for shopping Hipp Hardware Plus's Online Store for all your DIY and Home Improvement needs. Remember Hipps Help!