A standard pin backing is an 8 mm post with a single butterfly metal clasp (also known as military clutch) or a rubber clutch backing at no charge. If not specified the metal butterfly clasp will be used.
Other backing options include magnetic back, screw backing, safety pin, jewelry clutch, stick pin or tie tack. These backings are an additional fee.
In addition, you can turn almost any pin into a tie clasp, cufflinks, earrings, or keychain for an additional fee.