a novel connection for a thermoplastic neck to a stub neck portion of a container , comprising a curl on the stub neck portion and a complimentary groove on the neck which cooperate to permit a portion of the neck below the curl to expand when a plug of the closure cap , which is threaded onto the neck , is inserted into the neck . the neck and neck portion have interlocking projections to prevent the neck from turning and the neck and cap having a novel thread arrangement which insures that the plug will properly enter into the neck and provide a good seal which could be frustrated if the neck was permitted to turn .