Sharpie Professional Industrial Permanent Markers feature durable permanent inks that resist fading when put to commercial use. The ink is suited for industrial applications, including extreme heat (up to 500 degrees Fahrenheit). These permanent markers can be used on most materials including metal, glass, plastic, film, and foil. Marker Ink Type: Permanent; Marker Tip Type: Bullet; Marker Tip Size (text): Fine; Marker Color(s): Black.