Shop for Smart-X® sheets. Smart-X® is a lightweight, plastic material with surfaces of UV and weather resistant solid polystyrene and a core of expanded polystyrene that is moisture-resistant. It is a mono-material composite that meets the demand for ecological materials. Standard sizes available. Smart-X® is sold in cartons of 8-20 sheets. Stocked materials typically ship in 2-5 business days. Can’t find what you need? Get a quote.