Powder-coated brass Convertible cap Pressurized, performs in temperatures from -30F to 250F and underwater Pressurized ink cartridge performs in temperatures from -30F to 250F, underwater (up to 35 ft), and at any angle. Compact when you need it to be but still offers the comfortable writing experience of a full-size pen. Permanent ink writes through water, sweat, grease, and mud without clumping or smearing.