Like a regular Sharpie, but better.
 
"These Sharpie Industrial Permanent Markers feature ink that’s specially formulated to stay strong in the face of extreme heat conditions. Designed for industrial and laboratory users, the rich black marker writes on a variety of hard-to-mark surfaces including metal, glass and plastic. The durable fine tip creates strong, precise marks while the ink resists smearing and fading. Sharpie Industrial markers get even tough jobs done."