Abstract: A flow control structure such as is commonly referred to as a non-refillable closure which is primarily useful in minimizing the possibility of a bottle being refilled can be constructed so as to utilize two oppositely connected air traps in a passage which preferably also contains a ball-type check valve. The structure is intended to be mounted on the neck of a bottle so that in effect the passage serves as the bottle opening. When the bottle is in its normal upright position both one of the air traps and the check valve serve to prevent liquid from flowing into the interior of the container. When the bottle is in an inverted position in which at least part of the interior of the bottle is above the structure, the check valve is open as a result of the action of gravity and the air traps permit liquid to flow out of the bottle and air to flow into the container, but one of the air traps prevents liquid from flowing into the interior of the bottle.