The Uni Chalk Marker is perfect for writing on Blackboards.  The uni-ball Chalk Marker range is water-based and gives vibrant colours that are perfect for eye-catching designs. Ideal for non-porous Chalk Boards or glass in pubs, cafes and restaurants. They are also rain resistant, making them great for use outdoors. The ink can be easily removed from non-porous surfaces using a damp cloth or mild detergent. . Line width 1.8mm to 2.5mm, medium bullet tip. Available in a wide range of colours