PilotKakuno Fountain Pen of Biginners, Fine Nib, Light Green Body (FKA-1SR-LGF)

Is that ok if I use that pen with waterproof ink?

Which converter does it take? Pilot seems to have several of them, CON-30, CON-50, CON-70, and probably more.

Please provide size converter and refill required by this pen. Is it able to be filled with an eyedropper? Thanks.

What is a "Biginner?"