The Fellowes double loop wire binding spines (52540) are designed for use with the Fellowes Quasar Wire Binding Machine. However, they are also compatible with virtually any other 3:1 pitch twin loop or double loop wire binding system. These spines allow you to quickly and easily create professionally bound reports and presentations. Documents bound with these spines are both durable and elegant. Plus, double loop wire binding offers a secure and permanent binding for your documents.