Assertion: fountain pen | /r/HasAspect | piston
Facets:
Source sentences:
text: Fountain pens that do not require converters have a piston, aerometric, button or other filling system of their own.
text: The process of modifying a fountain pen that has an existing filling mechanism (such as cartridge/converter, piston, or aerometric) so that the entire body of the pen can be used as an ink reservoir.