A synthetic rubber, or elastomer, butyl rubber is impermeable to air and used in many applications requiring an airtight rubber. Polyisobutylene and butyl rubber are used in the manufacture of adhesives, agricultural chemicals, fiber optic compounds, ball bladders, O-rings, caulks and sealants, cling film, electrical fluids, lubricants (2 stroke engine oil), paper and pulp, personal care products, pigment concentrates, for rubber and polymer modification, for protecting and sealing certain equipment for use in areas where chemical weapons are present, as a gasoline/diesel fuel additive, and chewing gum. The first major application of butyl rubber was tire inner tubes. This remains an important segment of its market even today.