Write on the road, in the field, and in even in zero gravity. In any climate, in any weather, and in any position, our NASA-approved pen writes clearly and smoothly. Many traditional pens don’t even work on an airplane. The Trekker Space Pen’s pressurized ink cartridge works upside down, underwater, on wet or greasy surfaces, in extreme temperatures, and even in zero gravity. Includes a key ring and carabiner with breakaway lanyard. Black ink. Refill cartridges sold separately.