chips can be etched or printed, come in many colors, and may be highly reflective to enhance visibility at night. Some plastics are sensitive to ultraviolet light and the color and even composition can fade over time. ABS plastics are among the most durable for use as pet ID tags. Some tags use dye-sublimation to print images and artwork to aluminum tags. The image is permanent and resists fading and wear. 3D printing is also used to create tags from a variety of materials. Common metals used for pet tags are aluminum, stainless steel, and brass. Aluminum is by far (2.5 times lighter than stainless steel) the least durable of the three. Brass is a soft metal, and not as durable as any variety of stainless steel. It may also tarnish and turn a greenish color. Harder metals are more likely to retain their lettering after wear and tear. See also Ear tag Microchip implants Tattooing References External links American Humane Society's annual Tag Day New York Times Blog - Importance of Pet Tags Dog equipment Identification of domesticated animals