Features: Acid-free and waterproof, Professional waterproof technical drawing pens, permanent(Light fast), acid-free, non-fading ink, barrel window for convenient Size identification Perfect For: Artists, architects and engineers, adding detail to works of art, technical drawings and drafting, sketching and detailed lines, Watercolor underdrawings, illustrators and Designers, creating ultra-fine detail in artwork and Designs, and boundless creativity RICH INK: Each Acurit Waterproof Technical Pen has rich blank ink that is Perfect For permanent Application, is lightfast and acid-free, and will give a Professional and detailed look to your artwork WATERPROOF: You can Use Acurit Waterproof Technical Pens with any of your Watercolor based art and Paint; These pens will not run or smudge when Used with water Colors Variety: We offer a Variety of nib Sizes in a single or 12-pack including 0.2mm, 0.3mm, and 0.5mm; We also offer a Set of 6 assorted Acurit Waterproof Technical Pens that Includes 0.1mm, 0.2mm, 0.3mm, 0.5mm, 0.8mm, and 1.0mm Professional Waterproof Technical Pens Filled With Rich, Black Ink! The Acurit Technical Waterproof Drawing pen is Perfect For permanent Application. Acid-free, lightfast rich black ink. Acurit Waterproof Pens are Ideal For projects that require exhaustive detail such as technical drawings and drafting, but can also be Used for more artistic endeavors such as Watercolor underdrawings. Each pen Features a convenient window on the side of the cap for nib identification. Are you looking for the next step in detailing your Watercolor artwork? Look no further, grab a single or 12-pack of your favorite nib Size for you or a gift to you artistic friends. Grab the Assorted nib Size 6-pack to test out Each nib Size to find your favorite!