Copic Sketch Markers contain alcohol based ink that is permanent, non-toxic, and dries acid-free. Just like Copic Original Markers they are double-ended, one side features a medium broad nib for thick strokes, while the other side features a Super Brush nib that acts like a paintbrush in both feel and application. The markers are low odor, blend easily and are environmentally friendly. You never have to throw one away--they are refillable and the nibs can be replaced.