This Fisher Space Pen Refills SPR8 Pressurized Cartridge Brown Ink Medium is a top-quality product made in the USA. It features a pressurized refill that allows you to write in brown ink. The pen is made of brass and will fit most Fisher Space Pens including bullet and shuttle models. With this product, you can write upside down, under water, and through grease without any issues. It comes with a Fisher Space Pen guarantee that if you need a repair or replacement, you can simply return the product directly to Fisher. This ballpoint pen is perfect for collectors and individuals who value quality writing instruments.