Fisher Space Pen Pressurized Refill Blue Medium Fits Sensa Ballpoint Pens (Not For Sensa Pens That Have Parker Style Refills)
Special order item, Usually Ships Within 4 - 7 Business Days, Subject to availability.
Paul C Fisher developed the pressurized refill for NASA in 1965. It's still in use today on manned space flights because it performs when other pens fail. The combination of tungsten carbide ballpoint and jmzsttzryhthixotropic ink in a hermetically sealed cartridge pressurized at nearly 35 pounds per square inch allows it to write in freezing cold, boiling heat, underwater and at every angle - even upside down.