IDenti-pen features a dual point and leaves a permanent mark on most nonporous surfaces. One end is for details, with an extra fine plastic point that won"t break down. The opposite end is for broader lines, with a tough fiber point built for heavy use. Waterproof pen writes on leather, metal, wood, glass, CDs, plastic, and photographs. The ink is low-odor and resistant to water. Alcohol-based cleaners will remove ink from nonporous surfaces. IDenti-pen meets nontoxicity requirements..