As far as I remember, you should be able to tell if it’s a piston filler or a cartridge converter operated filling system on them. It should actually tell you on the webstore you are looking into. Like here, http://www.gouletpens.com/pkr1892552/p/PKR1892552 , at goulet pens, this one tells you that its a cartridge converter pen, and that the converter needs to be purchased separately