Liquitex Pro Paint Markers contain the finest quality professional acrylic paint, giving you greater control over your artwork. Fine tip measures 2mm and is replaceable. The pigments are processed using tiny reinforced ceramic beads, which give fine dispersion, strength and brightness. The paint is highly lightfast and conforms to at least ASTM II, with some colours conforming to ASTM I. It's water-soluble when wet, but once dry it is permanent and can be over-painted or varnished. The barrel of each marker indicates not just the colour it contains, but the opacity of that colour, so there is a choice of opaque, semi-opaque and transparent shades. To use, give the marker a good shake first, to thoroughly mix the paint. Then press the nib down a few times to start the flow. Markers should be securely capped when not in use, and stored horizontally.