Suitable for sketches or pen & ink drawings, these pens are unsurpassed in lightfastness. Pigmented Indian ink is waterproof and smudge-proof when completely dry. Ink formula is acid-free and ph-neutral, ideal for archival works. Set includes 4 black pens: extra-superfine (0.1mm), superfine (0.3mm), fine (0.5mm) and medium (0.7mm). Nylon tips provide crisp, clean lines. AP Seal, non-toxic.