A closure system includes a non-child resistant cap configured to screw on and off a container in a non-child resistant mode. The system further includes a child resistant element configured to be able to be assembled with the non-child resistant cap to convert the non-child resistant cap to a child resistant cap permitting a push-down-and-turn action to remove the child resistant cap from a container. A child proof element is separate from the child resistant element is configured to be able to be assembled with the non-child resistant cap to convert the non-child resistant cap to a child proof cap requiring a key to remove the child proof cap from a container.
