Designed specifically to fit Trodat Printy 4928 Rubber Stamps. 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. The 6/4928 replacement ink cartridge is available in black, blue, green, red and violet. Dry felt pads are suitable for special inks. Supplied as multiple pack of two.