Bel-Art Orange Oil-Based Tech Pen (F13384-0007) Soft tip writes on glass, metal, ceramics, plastics, paper etc Oil-based marking paint resists washing, weathering, mild acids and alkalis, and it operates within the temperature range of -46 degree to 65 degree C (-50 degree to 150 degree F) Withstands autoclaving at 121 degree C (250 degree F) Mark is approximately 1mm (0.040") wide