The most common materials used for signage are Medium Density Overlay (MDO), aluminum, foam board, and acrylic. MDO uses plywood materials with a resin fiber so it is lightweight, but sturdy. Aluminum is ideal for flexibility and sturdiness, especially outdoors in the elements. Foam board is a paper product that uses wood veneer to prevent warping, and is not as strong as aluminum or MDO, but is cost effective. Acrylic (plexiglass) is another great alternative that is clear, making it especially effective in light boxes, while enabling it to resist heat and other chemicals that can damage signs.