Rapidograph plotter pens

Hello,

I have several HP Pen Plotters including a DraftPro EXL (I started on a HP85 with an HPIB-Bus plotter at 8 years in the eighties). But I never managed to make these rapidograph refillable technical pens to work. I have several plotter points but I cannot figure out how to use them. I think I am missing a pen holder. I have an adapter but for rapidograph, but even as the technical drawing pens enter it, the nib is too short.

Anybody has some advice or pictures how to use the pens?

I send a photo of what I have..

Thank you
Hubertus / Switzerland - France

Attachment 456118