ISO 838 International Standard ISO 838 specifies two holes, with centers apart, and located from the nearest edge of the paper, and with the pair of holes positioned symmetrically along that edge. Each hole is to have a diameter of . Any paper format that is at least 100 mm high can be filed using this system (e.g., ISO A7 and larger). A printed document with a margin of 20–25 mm will accommodate ISO 838 filing holes. 4-hole or 888 A four-hole extension to ISO 838 is also in common use. Two holes are punched in accordance with the standard, plus two additional holes located 80 mm to the outside of the standard holes. The two additional holes provide more stability in 4-ring binders, while still allowing 4-hole paper to fit 2-ring binders. This extension is sometimes referred to as the "888" system, because of the three 8-cm gaps between the holes. Some 2-hole punches have an "888" marking on their paper guide, to assist punching all four holes into A4 paper. Konica-Minolta specifies that the holes should be from the edge of the paper for European 4-hole arrangements, contrary to ISO 838. ANSI paper sizes The United States and a few other countries use non-ISO paper standards, defined in ANSI/ASME Y14.1 and other intra-nation standards. Unlike ISO 838, there appears to be no well-established official specification for ANSI paper hole patterns, and instead they are de facto standards, established by custom and tradition. The diameter of the holes varies between manufacturers, with typical values being . The value is most commonly used, as it allows for looser tolerances in both ring binder and paper punching. The distance to the paper edge also varies, with hole-center-to-edge being typical. Konica-Minolta specifies for both two and three-hole variants in North America. US letter 3-hole system For the US letter paper size (), a three-hole standard is widely used. The holes are positioned symmetrically, with the centers apart. It requires paper formats that are at least high. US legal 4-hole system For US legal paper size (), a 4-hole system exists. It is still in use today, but is not as common as the 3-hole standard. The four holes are positioned symmetrically with centers apart. The four binding positions provide more support for the longer 14-inch side of legal paper. 2-hole filebinder Another standard also occasionally used in the US is a "filebinder"