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IRWIN STRAIT-LINE marking chalk delivers reliable performance for both interior and exterior applications. This 8 oz container of vibrant blue chalk produces crisp, visible lines on virtually any surface—ideal for layout work, framing, masonry, and construction projects. The standard formula resists fading and remains legible even in bright sunlight, making it an essential tool for professionals who demand accuracy and durability. Trusted by contractors and tradespeople for consistent results on job sites.