Abstract: The present invention provides a composition suitable for an air barrier such as an automotive tire innertube, innerliner, and aircraft tire innertube or innerliner, curing bladders, and other pneumatic devices. The composition comprises an elastomer comprising C4 to C7 isoolefin derived units; and a plastomer, wherein the plastomer is a copolymer of ethylene derived units and C3 to C10 ?-olefin derived units, the plastomer having a density of less than 0.915 g/cm3. In a desirable embodiment, naphthenic and aromatic oils are substantially absent from the composition. In another embodiment, a polybutene processing oil is present. Further, in yet another embodiment, a secondary rubber is also present such as, for example, natural rubber or butyl rubber, or a butadiene-based rubber.