Designed to fit the Trodat Printy 4910 and the Trodat Printy 4810 self-inking stamps. Comes as a multi pack of two. The ink is manufactured with a water base and contains no toxic substances, no acid, no formaldehyde, and no heavy metals. The ink is hygroscopic, meaning that it self regulates by absorbing the humidity of the surrounding air so that it does not dry out, allowing prolonged usage. Changing the ink pads in rubber stamps is simple thanks to the tabs that are positioned on the side of the stamp. The 6/4910 replacement ink cartridge is also available in black, blue, red, green and violet.