Binders are available for many binding sizes and two finishes. A "raw finish" or "A style" binder folds the strip twice on top and once on bottom, leaving the top edge encased and the bottom edge raw (to be covered by coverstitching). A "clean finish" or "B style" binder folds the strip twice on top and twice on bottom, leaving both raw edges of the binding strip encased. The photo below shows an A style binding: The photo below shows a B style binding: The photo below shows a B style binding being fed through the machine. Notice that both edges of the binding are turned under toward the center. Below is a close-up of an A style binder. Compare with a close-up of a B style binder, which has an extra folding "tube" for the fabric strip to pass through.