Ensure your favorite Fisher Space Pen soldiers on for plenty of zero gravity use for years to come. This replacement ink cartridge contains the same high-tech, black ink at a pressurized 40 PSI that's used on all Fisher Space Pens. Having been a no-go item on every manned US space flight since 1965, this ink cartridge has been shown to perform flawlessly on grease-stained paper, soaking wet paper (even works underwater), at zero gravity, at negative gravity, and under extreme temperatures ranging from -30°F to an insane 400°F. Also comes with a Parker pen attachment for use in Parker style pens. An extremely affordable, remarkably capable item that'll serve you well under all operating conditions.