Suitable for Trodat Printy 4921 rubber stamp to further extend the life of your stamp. 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. They are packed in 2 pieces in a convenient blister.