This pen leverages the energy from each push of the cap to inject air pressure into the ink cartridge, which allows the pen to write on challenging surfaces—it can write upside down, on wet paper, and in cold weather! Its compact size slips easily into a pocket, while its elastomer body is easy to grip even with wet hands or while wearing gloves, making this pen ready to use wherever you might be. The sturdy wire clip opens wide, allowing the pen to securely attach to both thin pockets and thick sheets of paper.