Feeds are designed to feed ink from the inside of the pen to the nib. Feeds are usually specific to a type of nib, that is, the feed must fit the underside of the nib and not leak. Most nibs have a unique size and shape.

As an example, the feed for the Zebra Manga G nib is different from the feed for the Nikko Manga G nib. That said, the feed for the Nikko Manga G also fits the Tachikawa Manga G nib and the Principal nib. 

Feeds are the second most important part in a fountain pen. The nib is the most important part, but without a good feed, the nib won't work very well. 

There are other nibs that fit our feeds. We are trying to develop a comprehensive list.