FKM Fluoro elastomer (Fluorocarbon) Viton® Dupont registered, known as Tecnoflon, Fluorel, Dai-El. Good for hot water, acid, alkali, oils, hydrocarbons and salt solutions, many aggressive chemicals, diluted acids, weak alkali's, mineral oils, aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, sunlight and ozone. -26°C to +205°C. Poor resistance to Ketone's and Acetone.