An ethylene/.alpha.-olefin copolymer comprising a component produced by a non-single-site polymerization catalyst and a component produced by a single-site polymerization catalyst, its preparation and use are described. The copolymer has an .alpha.-olefin content of 5 to 20 percent by weight and shows at least two CRYSTAF peak temperatures differing by at least 15.degree. C. and/or at least two DSC melting peak temperatures differing by at least 15.degree. C.