Paul C. Fisher developed the pressurised 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 ball point and thixotropic ink in a hermetically sealed cartridge pressurised at nearly a pound per square inch allows it to write in freezing cold and boiling heat, underwater and at any angle – even under water.

Black Ink Medium Size

Fits Fisher Space Pens Exclusively