Silicone rubber (SiR): noted for their ability to be used over a wide temperature range and for excellent resistance to ozone, weathering and aging. Compared with most other sealing elastomers, the physical properties of silicones are poor. Generally, silicone materials are physiologically harmless so they are commonly used by the food and drug industries. Standard silicones are resistant to water (to 100 °C), aliphatic engine and transmission oils and animal and plant oils and fats. Silicones are generally not resistant to fuels, aromatic mineral oils, steam (short term to 120 °C is possible), silicone oils and greases, acids or alkalis. Fluorosilicone elastomers are far more resistant to oils and fuels. The temperature range of applications is somewhat more restricted.