The flexible and durable brush nibs respond to instant changes in pressure or direction with a silky smooth, accurate and consistent ink flow. The deep black, archival quality Pigma ink is chemically stable, waterproof and fade resistant. There is consistent ink delivery to the brush sides and tip, with no smears, feathers or bleed-through on most papers. The fine brush nib is made of a tough porous polyethylene material, the medium brush from a tough nylon material and the bold brush from a tough plastic polyacetal material.