Suitable for Trodat Printy 4916 and 4916 Typo rubber stamps 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.