These Uni PX-20 Paint Markers can be used on almost any surface to leave behind shiny, opaque markings. It is both waterproof and fade-resistant for durable, long lasting results whether you’re using it inside or out. Each marker has a bullet tip so you can vary the line width based on how you hold the pen. The markers can be used on glass, metal, plastic, stone, wood and other surfaces. The oil-based ink produces opaque lines that are long lasting.