Refills for the Pentel Colour Brush Pens - Blue - Valve-activated for smooth flow, without leaking. Water-based and brightly colored dye ink flows easily, dries quickly, and produces transparent watercolor effects. Transparent Ink is great for wet on wet technique; Ink is not lightfast. Ideal for Manga, Illustration, Writing, Lettering & Drawing; Colours can be lightened & blended. Difference in pressure applied while squeezing the ink cartridge will result in variations in ink flow