Oakio Proshield decking is made using a combination (or 'composite') of both natural wood fiber and HDPE resin materials, and there is a layer around the WPC core to protect the surface, the layer is a kind of mixed multi plastic with additive like UV stabilizer, coupling agent, anti-oxidant and so on http://www.woodure.com/wpc-deck...-wpc-garden-decking.html