65101 BLUE CHALK REFILL 5LB | IRWIN STRAIT-LINE marking chalks have an innovative flip-top cap that keeps the chalk in the bottle where you want it. The flip-top cap seals the chalk in an airtight chamber, keeping out moisture and reducing the risk of clumping. IRWIN STRAIT-LINE introduces its new hi-flow nozzle cap for improved chalk flow on permanent staining chalks. The cap allows for quicker chalk fills and less clumping when using higher-density permanent staining chalks.