These water-based, non-toxic gel ink pens are high quality and acid free. Luxurious metallic colors flow abundantly from their rollers to produce sparkling effects on both light and dark papers. The pens also have crystal clear barrels, so you always know how much ink is left. Gel Xtreme pens are great for writing, embellishing, and decorating letters, cards, notes, and journals. They re also perfect for use with embossing powders because of their quick drying time. All Gel Xtreme pens have .7mm rollers, except for black, which has a .5mm roller.