Grizzly G1874 Improved Dowel Jig Automatically centers itself on round square or irregular shapes handles stock up to 2-Inch thick drill-hole sizes are 1/4-Inch 5/16-Inch 3/8-Inch 7 Handles stock up to 2-Inch thick Drill-hole sizes are 1/4-Inch 5/16-Inch 3/8-Inch 7/16-Inch and 1/2-Inch