ring binders

ISO Sizes

A4 pages are to be punched with two holes 80 ± 0.5 millimeters apart, 12 ± 1 mm from the nearest edge of the sheet, symmetrically located between top and bottom, and 6 ± 0.5 mm in diameter. (ISO 838)

Ring binders are 290 by 320 mm. (ISO 623)

North American Sizes

The length of the side along which the holes are punched is given first.

Page Size Hole dia. No. of holes Distance between centers
11 by 8½ inches ¼ inch or 516 inch 3 3½ inches
8½ by 5 inches ¼ inch 3 2¾ inches
8½ by 6 inches ¼ inch 3 3½ inches

A series of small ring binders called “memo books” have six rings. The paper is punched with 316 inch holes.

5 inches by 3 inches

6 by 3½ inches

6¾ by 3¾ inches

7¼ by 4¼ inches

Capacities
Spine
in inches
20-lb.
sheets
1 270
375
2 540
3 725
4 890
5 1100

Metals

Those with locks at top and bottom (double-lock rings) are generally of higher quality than those with only one or no lock.

Three styles of ring are used: round, elliptical, and D-ring. Elliptical rings are used in binders for a large number of pages: their advantage is that tabs are easier to read than they are with round rings. A D-ring metal is mounted on the back cover of the binder; it will hold about 25% more pages than round rings of the same size.

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