QUALITY MATERIALS - Durable aluminum construction designed for bookbinding use. The ideal choice for price books, menus, swatch books, photo albums, and other binding projects. EASY-TO-USE - Quickly bind loose documents and easily update or change out documents as needed. PRE-SIZED POSTS - Each Chicago screw has a post length of 5 inch and post diameter of 3/16 inch. Designed for punched holes 1/4-5/16 inches in size. PRE-SIZED SCREWS - Each Chicago screw has a screw head height of 1/16 inch and screw head diameter of 7/16 inch (including outer edges). POST & SCREW CONSTRUCTION - Post ends are closed and screws are threaded halfway through.