Original Cartier pen, the space pen. Writing underwater Completely sealed design allows clear note-taking underwater or in high humidity. Writing upside down Writes smoothly in any direction thanks to the pressurized ink, allowing you to write upside down. Heat and cold resistance Withstands extreme hot temperatures up to 100°C and very cold temperatures down to -35°C. Writing through grease Precision tip designed to penetrate oils and greases for writing on dirty or oily surfaces.