The present invention is directed to a peroxide curable rubber composition containing a butyl rubber polymer; an olefin polymer of ethylene, and at least one alpha-olefin, and optionally at least one diene; and between 2 to 5 phr of a peroxide curing agent. The present invention is also directed to a peroxide curable rubber composition containing a butyl polymer an EP(D)M rubber polymer, and a 1,2-polybutadiene polymer. Shaped articles made from the compositions find use as containers for pharmaceuticals, a condenser cap, a seal for fuel cells, a container containing electrolytes, rings, dampening devices, seals and sealants.