Automatically centers itself on round, square or irregular shapes. Handles stock up to 2″ thick. Drill-hole sizes are 1/4″, 5/16″, 3/8″, 7/16″ and 1/2″. Six hardened steel bushings are provided: 2 each of 1/4″, 5/16″ and 3/8″. You can drill two identical parallel holes without moving the jig. Easy to use!