Micron Black Fine Line Design Pen (.35mm – 03 size) by Pigma/Sakura.  Outstanding acid-free ink is archival quality, waterproof, waterbased, has no odor, will not smear nor feather when dry and will not bleed through most papers. Use for graphic art, sketching, pen and ink illustrations, awards, freehand art, calligraphy, as well as general letter writing and legal documents. AP non-toxic.