Similar to Wiro Binding, Spiral Binding attached the loose sheets by means of a plastic or metal plastic coil being passed through the punched holes.
A wide range of coloured coils are available. Most commonly used for the production of very thick price lists, road atlases, reference manuals and training manuals. Pages from spiral bound documents cannot come undone from the binding.
Spiral bindings cost somewhat more than Wire-o. They may be made of either plastic or wire and allow the printed document to lie flat and to double over.
One cannot add pages to documents once they are spiral bound. Also, rough handling may crush the spirals.