Abstract: The present invention relates to a container which has a removable screw cap. Said screw cap comprises an outer sleeve, a portion of which is provided with an internal screw-thread arranged to cooperate with an external screw-thread on the container, an inner cylindrical spigot or plug secured at one end within the sleeve by a bridge portion and arranged to fit inside the container, a plurality of flanges or rings on the spigot or plug, the said flanges or rings being arranged to make an interference fit with the inside of the container and a closure diaphragm closing the spigot or plug. The instant container is useful in diagnostic work, for example, to contain blood samples.