The Vortex Space Pen ballpoint pen has a sleek twist-activation mechanism that allows the point to be extended and retracted with a single turn. Designed for high performance and durability. Writes upside down, its side, through water, or in extreme temperatures, the Fisher Space Pen ballpoint pen contains a sealed pressurized refill (SPR) that will perform. Even if you aren't a space explorer, the Fisher Space Pen can guarantee you can record every event of your next adventure without a second thought. Refill: Pressurized 35 PSI Operating range: -35°C to 121°C