Silicone Rubber, 76-85 °IRHD. Silicone rubber having both methyl and vinyl substituent groups on the polymer chain. To meet UK Ministry of Defence Aircraft Materials Specification DTD5582A Grade 80.Applications: Particularly suitable in fluid sealing applications where low compression set is of prime importance in O-rings and gaskets. Can be used in contact with heavy mineral and certain diester-based oils within the quoted temperature range. Unsuitable for use in contact with petroleum based fuels, light mineral oils or greases derived from them. Excellent ozone resistance.