Channel letter signs are three-dimensional signs that are made of aluminum returns and back. Faces are made of Plexiglas with a plastic trim cap to hold the face to the return. Channel letters are illuminated either by neon or LED. Neon has been the illumination of choice for years because of its ability to be shaped and it's uniformity of light. However, in recent years LED has been coming on strong. This new technology allows for an 80% to 90% energy savings.