Nib Flexibility Scale

There is no industry standard for characterizing the flexibility of fountain pen nibs. To help the users of our website we have developed the following 5 point flexibility scale.

There are no definitive lines of demarcation where one grade stops and another takes over, but an amount of overlap, especially since there is so much difference in the “hand” of fountain pen users (the amount of force or pressure used during normal writing), even for the same user writing for different purposes and on different mediums.

The “wetness” or “dryness” (specific gravity) of the particular ink being used can also make a difference, sometimes significant.

So, while you need to keep in mind that there is no perfection here, the scale certainly provides useful guidance and information.

No Flex Basically no line variation at all.
Semi-Flex Sometimes called Tad of Flex. Just enough to provide some cushioning when writing. Conscious pressure is required to get any line variation at all.
Flex Obvious gradation to wider lines on the down-strokes. Pressure is required, but not to the extent of the above designation. Writers with only a “light hand” may not achieve the line variation.
Extra-Flex Gradation to wider lines with little to no conscious effort by the writer. Little force is needed to achieve the gradation and shadowing.
Triple Flex Extremely easy and wide line variation, often characteristic with calligraphy, copperplate or Spencerian writing.  The highest degree of flex.  Sometimes called “Wet Noodle.”