Cross Convenient  Fountain Pen Cartridges, Black, 6-Count (Pack of 6) (Pack of 2) Cross offers a wide range of ball-point refill sizes and colors; Selectip gel rolling balls, porous-points (felt tips), ball-points and document markers; 0.5mm pencil leads; specially formulated cartridges and bottled inks. Cross has re-invented writing instruments with jewelry-quality craftsmanship. We were America's first manufacturer of quality writing instruments, and that means that we've been making pens people use, depend on and enjoy for a long time. Cross Full Perpetual Warranty Guarantee. All Cross writing instruments are unquestionably guaranteed against mechanical failure, regardless of age. Should there ever be a problem, please call a Customer Service Specialist at 1-800-282-7677.