Montegrappa rollerball pens have a pen cap that is removed when you write with the pen. There are two options for rollerball refills. One has a top-hat shaped blue or black plastic piece on the end opposite the point (R5805). The other option is flat on the end opposite the point (R5804). A quick comparison of your old refill should enable you to order the correct replacement. Monteverde and Schmidt refills are a less expensive option.