Suitable for Trodat Printy 4724, 4740, 4924 and 4940 to further extend the life of your stamp. Two special grip zones allow a cartridge to be exchanged without touching the ink reservoir—for guaranteed clean fingers. The ink is water based 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 pads are available in black, blue, red, green and violet. Dry pads are suitable for special inks.