The new OTR.972 Inkredible ink is the original refill for the classic OTR.072 Inkredible markers. The alcohol-based heavy duty industrial ink is designed for any outdoor use and is ultra fade & UV resistant. The deep black & dark red inks are weather-proof, extremely permanent, and normally used against the ravaging effects of the elements like rain, snow and sunlight. The Inkredible ink etches into the surface. The OTR.972 Inkredible ink stands out from commonly available permanent inks. It penetrates the surface it is used on, resulting in a truly permanent, weather-proof, and light-fast mark. OTR.972 Inkredible ink Etches deep into the surface resulting in a nasty stain that is hard to remove. Recap after use and get on the run!