Irwin Strait-Line Blue Permanent Staining Chalk Line Chalk, 6 oz. is specially designed for exterior use in extreme conditions, providing a durable and highly visible marking solution. This chalk stains surfaces to ensure your lines remain visible even after weeks of exposure to weather and jobsite wear, significantly reducing the need for spray sealants. With a permanence scale rating of 4, it long-lasting performance in a vibrant indigo blue color. The product comes in a convenient 6 oz. bottle, making it easy to apply for all your marking needs. Model Number: 4935518