Microperm pens can be used to make precise long-lasting marks on test tubes, circuit boards, diamonds, cellophane, wood and glass, plastic, metal, or wherever there is a need for waterproof ink that will write on non-porous surfaces. Diamond cutters can use Microperm to make minute markings on rough diamonds to ensure exact cuts.Chemically stable, and waterproof. Low odour and fulfills non-toxicity requirements. Permanent adherence to most surfaces. A fine line nib with a protected tip that will not split. Alcohol based cleaners will remove ink from non-porous surfaces. Writes on diamonds, glass, wood, cellophane, plastic and glossy sheets, CDs, photographic and x-ray film, paper and metal. Set contains one of each pen: 01 (0.25mm), 03 (0.35mm), 05 (0.45mm).