They appear to be made of quality steel. Carefully cut into plastic. The price is very reasonable. Separate containers, each containing a wrench and a spring. To the person who gave the bad review: It's a Forstner-style beat! It is designed for plastic, soft metal and thin wood. Only the inner surface can be drilled. A deep hole in wood requires a spatula (for these diameters). By the way: The spring makes the cut a little flatter, but can help to push out the dowel without unscrewing the saw blade for cleaning. For your health.