Hardcover or softcover, hidden spiral.
With Wire-O binding you can accommodate pages and inserts of varying thicknesses, including dividers or index tabs made from heavy cardstock. The Wire-O binding method utilizes pre-formed pairs of wire loops that run along a C-shaped unit. These wire loops are inserted through holes that have been punched through the book’s cover and pages. The loops are then crimped closer together until they form a perfect circle, thus securing the cover and pages as an assembly, yet allowing them to open freely.