Twin loop wire, also called “duo-wire” or “wire-o,” is a versatile binding spine that pairs security and durability with style and affordability. It has signature hole patterns of two holes per inch (21 holes per letter-sized sheet) or three holes per inch (32 holes per letter-sized sheet), depending on the thickness of the document that is being bound. Documents between 3/16″ and 9/16″ thick (5-120 sheets of standard 20 lb bond paper) utilize the 3:1 pitch pattern (three holes per inch), and documents between 5/8″ and 1-1/4″ thick (110-250 sheets of standard 20 lb bond paper) utilize the 2:1 pitch pattern (two holes per inch).
In order to create the secure, tamper-proof finish that wire binding is known for, a specialized device called a wire closer is used to pinch the open ends of the wire together and complete the bind. The majority of wire binding machines include a built-in wire closer, however they are also available as separate units. Since duo-wire comes in two different pitches, each machine is specifically set up to punch either 2:1 or 3:1 pitch hole patterns. If you are unsure as to what size documents you will be binding or want the ability to punch both 2:1 and 3:1 pitch hole patterns, you may want to consider a combination or modular machine that includes both punches.
Twin loop wire is available in sizes ranging from 3/16″ (5-20 sheets of standard 20 lb bond paper) to 1-1/4″ (240-260 sheets of 20 lb bond paper), and in 11 standard colors. Because of its popularity, duo-wire is sold in pre-cut lengths as well as bulk spools, which makes it the most economical wire binding spine.