Fisher Space Pens are built for more than just outer space. The fact is, due to the patented sealed and pressurized ink cartridge, they 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. The sealed and pressurized ink cartridges last three times longer than the average pen with an estimated 100-year shelf life.