Montana's ACRYLIC Paint Marker Refills contain high quality water-based paint made with a high concentration of lightfast pigments that cover well. It is water-proof and abrasion-proof and can be used on almost any surface, indoors and out (though when using outdoors it should be varnished). The paint is safe to use, it is solvent-free, ACMI approved and each marker carries the AP mark of non-toxicity. It can be used to refill your markers or for airbrushing, mixed media, and brush applications. The line of 180ml ACRYLIC Paint Marker Refills comes in 24 colors that match to corresponding colors in the Montana GOLD spray paint line.