Irwin 4935524 Marking Chalk Refill, 4 lb, Indigo Blue, PermanentIrwin 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. Unit: EA UPC: 024721999320 Model Number: 4935524