Abstract: A wire ring binder is formed of a continuous segment of wire bent in an undulating form in which finger sections extend in a parallel array from a colinear array of backbone sections. The width of the fingers approximates the length of elongated apertures in sheet material which is to be bound. In the case wherein the spacing between apertures is equal to the aperture length for maximum strength and ease of perforation, the width of the fingers is slightly less than the spacing between fingers to provide clearance in the apertures. Each finger is formed of two sections of wire joined together by an arcuate terminating section which overlaps into the spacing between backbone sections.