High density polyethylene (HDPE) lumber is made from recycled plastic materials (and can be recycled again). Longer lasting than most traditional woods, it is virtually dent-proof, moisture-proof, rot-proof, and insect-proof. Because of its slippery nature, horses don't like to eat it. It is available in a variety of colors and is extruded into traditional lumber sizes with the traditional lumber grain. It will self-extinguish in a fire if fuel is withdrawn. It can't splinter, doesn't crack and is maintenance free. Wow - this one's a shoe-in for those who don't want wood in their stalls.