Rite In The Rain Trekker Pen WRITES THROUGH: The permanent ink writes through water, grease, and mud without clumping or smearing. PRESSURIZED CARTRIDGE: All-Weather cartridge is pressurized, writes in temperatures from -30F to 250F, under water (up to 35 ft), and any angle. PROPRIETARY INK: The ink and delivery system used exclusively in Rite in the Rain Refills will write without skipping in extremely wet conditions far better than other comparable all-weather pens. INK DELIVERY: Tiny pockets in the pen's tip will deliver ink in the worst conditions without allowing water or air back into the Cartridge. RITE IN THE RAIN NOTEBOOKS: The most ideal pen for Rite in the Rain All-Weather Notebooks.