Abstract: A lock assembly includes a lock shell, at least first and second key plugs, at least first and second tumbler means, and a key for operating the first and second tumbler means. The lock shell has a front end, a rear end, and an accommodation hole extending from the front end to the rear end. The first and second key plugs are aligned axially and are mounted rotatably within the accommodation hole of the lock shell. The first and second key plugs respectively have first and second key ways. The first and second tumbler means are used for positioning respectively the first and second key plugs against the lock shell when the lock assembly is in a locked position. The key can operate the first and second tumbler means so as to rotate the first and second key plugs simultaneously.