Used most commonly for top-binding letter size 8 ½" x 11" paper, as well as custom, unique binders, scrapbooks, and swatch books, our 2-ring binder mechanisms are a popular option. Made of a durable metal, these binder spines do not have any boosters, which means your sheet size is not limited. On each end are holes that allow you to use a rivet setter tool to set rivets, which is the most popular way to make ring binders. Spacing between rings