The Pentel Chalk Marker has a valve-activated flow that helps to prevent against blobbing or leaking. The SMW26 is ideal for use on chalk boards and non-porous surfaces such as glass. It is suitable for both indoor and outdoor use making it perfect for menus, advertisements, timetables etc. It has a semi-permanent formula which won't run off in a light shower but can be removed with a wet cloth. Its chisel-style tip enables you to create a variety of effects with an approximate line width of 4.0mm to 2.0mm