Fisher Space Pen Ink Refills for Fisher Space Pens, Medium Point, 0.7 mm, Black

Utilizing sealed and pressurized ink, this Fisher Space Pen refill makes it easy to keep your favorite pen going strong. Use it to write in just about any location or position, even upside down or underwater. Thixotropic ink writes in unique conditions. In the freezing cold, boiling heat, underwater and at any angle - even upside down! Famously writes for a long time. Will write for a distance of 2 to 3 miles, or approximately 15,000 feet. Precision machined ball and socket to prevent leaks. Also delivers instant uniform ink flow.