Durable solid steel construction provides years of long life performance that will not deflect under pressure of drilling. With a hybrid flat hex set screw in the body, it provides a tight fit to withstand vibration but provides ease of replacement of set screw with use of common flat head screwdriver. 3/8" round arbor for use with IDEAL® Bi-Metal Hole Saws 9/16" to 1-3/16".