Fisher Space Pen Pen Refill

Ballpoint pen refill fits Fisher Cap o matic Space Pen to write in almost any environment. The combination of a tungsten carbide ball point with thixotropic 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 any angle. PR4 Medium Point refill for S251 Cap o matic ballpoint space pen Pressurized cartridge allows pen to write underwater and upside down Black Ink Functions in water and at temperatures from 30F 35C to 250F 121C