Co-vulcanizable compositions comprising (A) 55-85% by weight of a fluoroelastomeric copolymer of vinylidene fluoride with perfluoropropene and possibly tetrafluoroethylene; (B) 45-15% by weight of a copolymer of tetrafluoroethylene and propylene; (C) 0.7-2.5 parts, per 100 parts of (A)+(B) blend, of a bisphenolic compound; (D) 0.3-1.5 parts, per 100 parts of (A)+(B) blend, of a quaternary ammonium, phosphonium or aminophosphonium organic compound; (E) 0.4-5 parts, per 100 parts of (A)+(B) blend, of an organic peroxide; (F) 1-5% by weight, as referred to (A)+(B), of a peroxidic cross-linking coagent.