I use a variety of plastics such as abs and poly plastics that range from 020 – 030 thickness. These plastic molds can be used to cast plaster, concrete, clay, wax, some cool setting resins and compo. The strength of the plastic varies with the size of the mold - the larger the mold, the thicker the plastic. Plastic molds can last for years and create beautiful reliefs for walls, 3-D murals, ceilings, furniture, cabinetry and fine art pieces.