An electrical wire having a conductor and a covering disposed over the conductor wherein the covering has a thermoplastic composition. The method comprises the following steps, which method comprises passing a gas into a means for forming excited andor unstable gas species, typically an atmospheric pressure plasma or the like and treating the gas such that, upon leaving said means, the gas comprises excited andor unstable gas species which are substantially free of electric charge. The mandrel tip has a passage through which plastic is extruded to form a wall that divides the extruded tube into separate chambers. Also provided for is an element suitable to guarantee proper positioning between the cover part and the cup part in the assembled position, and elastic locking elements preventing the shaker from opening after preparing the cocktail.