Wire-O Binding/ Double Wire Binding
There’re plastic wire-O/metal wire – O binding
Wire-o double wire spiral binding, also called twin wire, use a continuous hinge of double loops of wire to hold the book covers and leaves together.
Wire-o / doublewire binding is recommended for: upscale brochures, reference manuals, cookbooks, and calendars. Advantages: lays flat and looks professional. Disadvantages: the wire is metal and can bend if enough pressure is applied where the plastic wire will bounce back to its original form.