The cap for this Space Pen is an actual .375 H&H Mag Shell. A special gift for the hunter or outdoor enthusiast. The portion of the pen that contains our pressurized refill cartridge is plated with Copper Zirconium Nitride. The combination of this portion of the pen, which is what appears to be the cartridge when closed, along with the Nickel Silver Cartridge/Casing. The 375 Space Pen measures 133 mm (5.25 inches) opened, 95 mm (3.75 inches) closed and contains a #PR4 Black Ink, Medium Point Pressurized Fisher Space Pen Refill.