Teacher's Stamp delivers a red winking smiley face with the red words, "Good Homework." It works like a small printing machine. Just press down, and it prints, delivering hundreds of thousands of clear, crisp impressions. Stamp is self-inking from built-in stamp pads that contain nontoxic, water-based inks. Cartridge can be easily and cheaply replaced in seconds. Clear index window provides easy identification. Die-plate size is 13/16 x 13/16 in.