Silicone elastomers or silicone elastomerics most often refers to silicone-based polymers that have been vulcanized. Although technically incorrect, the term “silicone rubber” is often used since it is more intuitive and descriptive. Silicone elastomers or silicone rubber materials are readily available in a variety of forms, such as solids, open cell foams, closed cell sponges, thermally conductive, and electrically conductive. Their natural colour is off-white/yellowish, but formulations often include opaque, coloured fillers. Although relatively weak at ambient temperatures, their retention of properties and overall performance at both higher and lower temperatures is very good – and can, to some extent, be moved in either direction by formulation. They have very good chemical and UV resistance but can be prone to (slow) hydrolysis in high pressure steam and in the absence of oxygen at high temperatures. They are also very permeable to gases.