Space Pen

An AG-7 Astronaut Space Pen in presentation case.

The Space Pen (also known as the Zero Gravity Pen), marketed by Fisher Space Pen Company, is a pen that uses pressurized ink cartridges and is able to write in zero gravity, underwater, over wet and greasy paper, at any angle, and in a very wide range of temperatures.

Astronaut Walter Cunningham, Apollo 7 lunar module pilot, writes with space pen as he is photographed performing flight tasks on the ninth day of the Apollo 7 mission.
Nib end of gold colored pen body with refill laid into alignment underneath
Close up of a Fisher Space Pen body showing knurlings with removed refill adjacent
Three stacked pen refills with similar fittings for comparison
Fisher Space refill at bottom compared to similar Parker-standard and generic (non branded) Parker type at top