The factory produced a number of dual-coil has the following advantages: double-loop bound books, paintings, books can turn 180 degrees flat. * Binding to 360 degrees after the overturn. * Binding process simple and fast. Calendar, desk calendar, notebook are essential to work fine steel ring world. * Binding sound, the album will not fall off, rims the same type. * A variety of colors and beautiful new high grade steel ring clad steel ring made of plastic powder, the surface of high-brightness, bright color, center elastic strength of the soft and hard steel.