According to Fellows it is 1/4" comb bind
With a good supply of binding spines, your binding machines are always ready to use when you need them. On Time Supplies carries binding spines in a range of capacities and styles, including Fellowes plastic comb bindings. Thanks to fast shipping and bulk pricing from On Time Supplies, you always have binding spines when you need them. If you need more information on the supplies featured at On Time Supplies, or on GSA pricing, call us toll free at 1-866-501-6055. We're happy to answer any supply questions.