This is one of the larger converters that Pilot makes. And while the filling system sucks, it can hold a lot of ink if you syringe fill it.

But when I tried to fill it with the push vaccum mechanism I could never get a decent fill .

It is a little bit weird, but it is the thing I wish Pilot used in all of their pens, simply because it can hold enough ink for it to not be a problem for most people.