Silicone rubbers are substances whose chemical skeleton is made up of extremely stable silicon – oxygen linkages. Silicone rubbers are chemically related to quartz and glass and many of their excellent properties are similar to those of the latter materials. The molecular structure of silicone avoids the rigidity of the organic groups on every atom and during vulcanisation they are cross linked to form a three dimensional, flexible, rubber like substance. Inorganic fillers are embedded in the latticework structure and have a decisive effect on the general properties due to the reciprocal action between the filler and high siloxanes. As with other kinds of rubber, the physical and chemical properties of silicone may be varied by the appropriate selection of filler and catalyst.