€¢ For interior and exterior use €¢ Marks are temporary €¢ Provides great visibility €¢ Easy-to-open flip-top cap €¢ Hi-flow nozzle cap on permanent staining chalk >> 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(r) STRAIT-LINE(r) 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. Micro-fine for more marking power; interior or exterior use. Marks are temporary and provides great visibility."