Blackline BL816 8 oz Blackline Water Proof Chalk Refill Water proof, will not wash away even under heavy downpours Out performs traditional chalk with less smudging creating a clean, easy to read line Resists being blown away, layouts can be done in windy conditions For wet or dry application, simply remove standing or excess water then snap line Saves time because layouts, pour lines, etc, will never have to be redone