Heat shrinkable thermoplastic compositions are prepared by blending an ethylene copolymer resin with a rubber and dynamically vulcanizing the rubber. The ethylene copolymer resin is a copolymer of ethylene with an alkyl ester of an alpha, beta monoethylenically unsaturated monocarboxylic acid as well as copolymers of ethylene with the acid per se. The preferred copolymer is ethylene-vinyl-acetate copolymer. The preferred rubber is halogenated butyl rubber. Uncured rubber can be included in the composition.