Various Ink refills are available in all 358 Copic colors, and are universal for all marker styles. Additionally, empty ink bottles are available, so you can mix your own custom colors. Alcohol based ink is permanent on most surfaces, non-toxic, and dries acid free. Guaranteed color consistency with each bottle. Angled, dropper style tip makes it easy to refill markers and works well for dripped effects. Measurements are marked on the bottle, so you know exactly how much ink you've used.