Abstract: Closure for containers, comprising a locking ring (1) which in situ surrounds the container along the whole of its outer periphery. At least one area of the container closure comprises means which allow a substantially reversible increase in the circumference of the locking ring. The container closure also comprises at least one lock-release part (2) on the radially external side of the locking ring, and which in at least one end is fastened to or constitutes an integrated part of the locking ring (1), and which under the influence of a force results in an increase in the circumference of the locking ring (1). There is hereby provided a closure system for containers whereby the container can be opened even by very weak hands, and whereby it is subsequently possible to effect a closing of the container so that this is closed tightly. The opening and the closing are effected without the use of tools.