The Fisher Refill Black Bold is a refill for tactical pens in a parker-style. If you use your tactical pen a lot there will be a time when you start looking for a new refill. This Fisher refill contains black, thick pressurized ink.
Paul C. Fisher developed the pressurized refill for NASA in 1966. Today these refills are still used on manned space flights because it will perform when other refills won't. Because of the combination of substances and ink in a hermetically closed cartridge this refill will continue to function in the cold, heat, under water and even upside down.