IRWIN's 4 lb. STRAIT-LINE® Indigo Blue Permanent Staining Marking Chalk delivers consistent performance for chalk reels and layout tools used in demanding applications. Its fine texture helps support smooth dispensing and even coverage, while the high-visibility blue color improves line recognition during installation, framing, and alignment work. Built for contractors, tradesmen, and homeowners, this marking chalk provides a reliable solution for projects requiring accurate and long-lasting layout lines.