Pigma Gray & Black Micron Brush 10 Piece Set features archival-quality ink for use in acid-free environments. They are chemically stable, waterproof, fade-resistant and produce no smears, feathers or bleed-through on most papers. Package includes ten pens in assorted grays and blacks in sizes 01 (.25mm), 05 (.45mm), 10 (.60mm) and BR.