The self inking engineer stamps are available in the 1 1/2" size. Larger stamps are available on request but are somewhat bulky. The self inking engineer stamps have a built in stamp pad that the stamp die is rotated against and inked each time it is used. The ink colors are available in black, red, blue, green and violet. These stamps will last for thousands of impressions and replacement pads and inks are available. These engineer stamps are not suited for use on non porous surfaces.