An annulated tubular sheath which is split down a longitudinal section thereof. According to the invention, a longitudinal strip of the sleeve is made of a flexible material and is disposed in an angular position of 5-180 degrees in relation to the longitudinal section or is disposed in the region of the sheath in which the longitudinal section is made. Preferably, the flexible material is a thermoplastic elastomer. The invention also relates to a method for producing a sleeve by extruding a plastic material, a longitudinal strip made of a flexible material obtained by co-extruding an elastomer material. A device for carrying out said method comprises an extrusion head provided with an insert for placing the co-extrusion in a stop position on a die in order to block the flow of the extruded plastic material and to enable the flow of elastomer material.