I get asked pretty often about which Pilot converter to choose for a given pen, with ink capacity usually as the motivator for making the choice. So I decided to dedicate a whole video to the 5 different options available today from Pilot. I broke it into two parts: Part 1 is an overview that will provide you with the takeaways from my testing, and Part 2 is the nitty-gritty showing how I actually did my measurements. I compiled them into a playlist so you can easily skip from one vid to another.
There are 5 different options for getting ink into your Pilot/Namiki fountain pens. It should be noted that older versions of today's available pens may be limited in converter selection, though I'm not knowledgeable enough of all vintage pens to say for sure what those are. I do know that all of the modern Pilot and Namiki pens available in the US as of this posting will accept all 5 of these filling mechanisms, with the exception of the Con-70, which only fits in the Pilot Custom 74 and Pilot Metal Falcon (perhaps others, but I'm not aware of any more).
Here are the 5 different filling mechanisms, with the ink capacities that I measured in my test. It should be noted that I didn't fill them to the absolute brim, as that would not be practical since it would gush out when you go to put the filling mechanism on the pen. I filled them all to an equal level to give adequate space for placement onto the pen. That's just how I decided to do it.
Pilot/Namiki Cartridges, proprietary to these brands of pens, hold about 0.9mL of ink
Pilot Con-40, the most common and recognized of the group, it's a twist/piston converter with an agitator. This converter has an ink capacity of .61ml.
Pilot Con-70, the big daddy. This monster button-filler is only accommodated by the larger Custom 74 and Pilot Metal Falcon, and comes in silver on the pens, yet replacement converters sold are black, as pictured here. This one will yield about 1.0mL of ink.
What does all this mean?
When it comes time to actually make a decision about which converter will be suit your needs for your Pilot/Namiki pen, there are a variety of factors involved such as compatibility with your pen model, price, functionality, ink capacity, price, and ease of cleaning.
I decided to focus mainly on ink capacity for this blog post to keep myself focused, so with that in mind, unless you're fortunate enough to have a pen that accommodates the Con-70, the Con-40 or refilling ink cartridges will get you the greatest ink capacity. They both have their drawbacks though, to fill cartridges you'll need something like an ink syringe to be able to do it, and it's an extra cleaning step involved there. Removing the agitator will gain you about 0.1mL of ink capacity, but it will also be more likely to have flow issues if the ink hangs up in the back of the converter (which is exactly why Pilot puts that agitator in there, to prevent that).
Like most things in life, it all comes down to compromise. There are some slight tradeoffs going from one converter to another, and none of them are ideal for everyone, which is likely why you see the broadest range of converters in this brand than any other modern pen brand. But at least now you are a little better educated about how ink capacity factors in to your converter choice. If you have any questions or need clarification, just let us know!