The original Bullet Space Pen was conceived in July of 1948. Paul Fisher was soon machining a new pen design shaped from solid aluminum. It became the first Fisher ball point pen, the #400 Bullet Pen, is arguably the most popular pen of the twentieth century. This pen is now all brass with a Black Titanium Nitride finish.When closed, the Bullet Space Pen is the perfect size to carry in your wallet, pocket, purse, car glove box, organizer or toolbox. When open it's a full sized, evenly balanced writing instrument. The patented ink cartridge was designed by Paul Fisher for NASA in the 1960's enabling it to write in temperatures from -30 to +250 degrees Fahrenheit, under water, in zero gravity, at any angle, even upside down.