65105 ORANGE CHALK REFILL 5LB | IRWIN STRAIT-LINE Marking chalks have a newly engineered flip-top cap that keeps the chalk in the bottle where you want it and stops it from spilling out in areas that you don't. The flip-top cap, available on all IRWIN STRAIT-LINE chalk bottles, seals the chalk in an air-tight chamber, keeping out moisture and reducing the risk of clumping.