More Info About Letter Size Binder Mechanisms
Letter size, sometimes called US letter, is the most popular paper size in North America, including the United States, Canada, and parts of Mexico. When you pick up a ream of paper from the store, you will almost always be looking for a letter-size sheet. These pages measure 8.5 inches wide and 11 inches high (or 216 millimeters wide and 279 millimeters high). Sometimes they are called size "A", however, this is not to be confused with A4 which is the closest ISO (international system of paper sizes), but is slightly taller and narrower.
These ring binder spine mechanisms are made for letter-size 11" binding edges. They have three rings with a standard hole spacing of 4.25 inches between the rings. They are available in silver, matte black, or a gold/brass finish. All options feature boosters on the ends that allow for easy opening of the rings without risking damaging the rings themselves or the closure integrity. They have two rivet holes, one on each end, that are spaced 3/4 inch from the short end, and 9-1/2 inches from each other. The length of the base itself ranges from 11-1/4" to 11-3/8", varying only slightly based on the ring size.