Moisture tight closure and container systems

A closure and a container having a moisture tight sealing engagement with each other, said closure being either a child resistant or non-child resistant closure, comprising:

• a container having a side wall, an upper end with an open mouth over which said closure is received, and locking members on said container adjacent said upper end;
• an interior wall on said side wall of said container having detent projections extending inwardly into the hollow interior of the container, ends on the detent projections being spaced from one another in a circumferential direction and to define spaces between adjacent projections;
• a closure having a top wall adapted to extend across the mouth of said container and a depending skirt wall, a sealing plug extending downwardly from said top wall and having a depending wall for insertion into said open mouth of said container;
• said depending wall having an outwardly projecting annular sealing surface, the annular sealing surface having a diameter substantially larger than an inner diameter defined by the projections,
• portions of the annular sealing surface expanding into the spaces between adjacent projections as the sealing surface is being pushed down past the projections or is being pulled upwardly past the projections, said sealing surface extending below said detent projections to hold said closure onto said container and to engage said interior wall below said projections to provide a moisture tight sealing engagement of said closure with said container, said projections holding the closure on the container.