Ebonite

So underneath the nib, the black, normal- normally it's black, sometimes it's red, sometimes it's clear plastic.

The piece of, the piece of plastic or Ebonite that goes underneath the nib is called the feed, and that is what delivers the ink from the filling system, um, whether it's the cartri- whether it's the cartridge, the converter, the piston, or the, um, ink chamber if you're using something like a vac filler or an eyedropper that holds the ink in the barrel.

The ink will flow down the feed through the feed line, which is the, the slit cut into the feed or the channel cut into the feed 'cause sometimes there's more than one.

And it will flow through the feed line, and there are also fins sometimes on the underside of the nib that also holds ink.