Abstract: A closure for a container, e.g., a tube, for a sample, e.g., a biological sample. The closure comprises a seal and an adapter to mount the seal onto the container. In one embodiment, the adapter is a cap that is inserted over the mouth of the container. The adapter is typically cylindrical in shape and is characterized by having a circular top with a cylindrical side wall projecting from the top. The top of the adapter has an opening formed therein. The opening generally surrounds the axis of the cylindrically-shaped adapter. The opening has dimensions sufficient to accommodate a sampling device for obtaining access to the contents of the container. The seal depends from the surface of the top of the cap that faces the interior of the container. The seal has a peripheral portion enclosing an interior portion. The peripheral portion has a side wall and a bottom wall.