Our round ink cartridges for Trodat Professionals stamps are great. 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. These ink pads are available in an array of colours: black, blue, green, red or violet. As well as dual colour red and blue pads, which are perfect for date stamps.