Sealed and pressurized, this refill will help to write underwater, upside down, at any angle, from -30 degrees Fahrenheit, -35 degrees Celsius to plus 250 degrees Fahrenheit, 121 degrees Celsius. It is 3 times longer than the average pen and is environmentally friendly. It fits most of the Fisher Space pens. Also comes with an adapter so that it can fit in any other ballpoint pen as well.