The Keson ProChalk Ultimate Permanent Waterproof Chalk Dye (5 oz.) in blue is a specialized marking solution designed for professionals requiring durable, weather-resistant lines. Its permanent and waterproof properties ensure that markings remain visible and intact even when exposed to moisture or harsh conditions, reducing the need for re-application. The 5 oz. container provides a practical volume for regular use. The part number for this item is 5BD.