I think it's carbon steel and I think it's strong. No, not this one. The bits work and they made some holes. But they bend so easily! In fact, they came out of plastic with a slight bend. You can bend them back into shape with your hands. However if you are looking for a real dump without the potential for wallowing. maybe it's not the best buy. But if you're just looking for a hole in a thick material (wall) and don't care how perfectly round it is, then they'll get the job done.