Bullet Space PenFisher Space Pens are built for more than just outer space. These pens will write in just about any condition and on almost any surface. Underwater or over grease. Extreme temperatures ( 30 to +250 F 35 to +121 C). Upside down or floating in a gravity free zone. Their sealed and pressurized ink cartridges last three times longer than the average pen with an estimated 100 year shelf life. When closed, the Bullet Space Pen is the perfect size to carry