Sketch Markers are the most popular of the Copic Markers. They are excellent for all forms of illustration, design, scrapbooks, fine art and more. These double-ended markers have an alcohol based ink that is fast drying, permanent, acid-free and non-toxic, and come in a vast variety of colors. They are refillable, constructed in a unique design for a more comfortable grip, and so they will not roll away from you. They can also be used with the Copic Airbrush system. Durable polyester nibs come in Medium Broad and Super Brush - a soft, flexible, fast-flowing brush for delicate or bold expression. Sketch markers have a 3-year shelf life and are guaranteed for color consistency. Available in over 300 colors.