Pelikan rollerball pens fit Pelikan rollerball refills, or an option recently introduced by Monteverde.
Pelikan rollerball refills are offered in black or blue ink with a fine or a medium point.
Monteverde Wide Writer refills were designed specifically for Pelikan rollerball pens. This less costly option comes in blue, black AND blue/black ink and is offered with a medium or broad point. If you haven't tried them, please do.