Rollerball pen refill with blue ink delivers a rich, sophisticated color for an optimum writing experience that's convenient and practical. Medium-point nib creates bold, solid lines for greater visibility on pages. Smooth-flowing design lays down effortlessly to produce consistent, fluent lines. Easy-to-use design allows you to quickly replace your depleted pen for quick, simple use. Ink cartridge is designed for all Parker rollerball pens (sold separately).