This special Edition Cap-O-Matic Space Pen has the same pressurized ink refill cartridge used on the Apollo 11 Mission. It defies gravity, writes in the harshest of environments, and is still used on all manned space flights today. They will write upside down - at any angle, under water, through grease, extreme temperatures (-30 to +250 degrees F), on almost any surface, three times longer than the average pen, and of course in the gravity free vacuum of space and these pens are lifetime guaranteed!