Yes. I used some, although I bought them from someone else.
They are pretty nice in that they have a clear 'window' so you can see the ink level.
They have threads that I turned off and used my own.
Mmmm, well that depends on who you ask. I believe it does hold a 'bit' more but some people claim it holds twice as much.
I liked them because the mechanism is beautifully made, it has little o-ring seals and the twist piston gives a nice firm action. And of course the novelty of the ink window
There is a LOT of work to use these and they are not cheap enough to learn on.
On the plus side, they can be completely stripped down and the brass is even thick enough to take fine threads.