PenGems standard ballpoint refill cartridges hold the same ink that you love in your pens, but in a medium size. You can stock up so you'll never run out of ink. They are D1 ballpoint refills and will fit a wide range of compact and multi-function pens. The writing length of these refills is measured at 350 meters.
Your pen will come with black ink installed and an extra refill cartridge.