A threadless cap for closing a potable liquid bottle is provided. The potable liquid bottle has a neck with an upper edge defining a discharge opening. The threadless cap comprises a lid for overlying and sealingly engaging the upper edge of the neck. The lid includes a tension ring for retaining the cap on the neck of the bottle, the tension ring having an inwardly extending rib for engaging the neck of the bottle. The threadless cap also comprises a skirt depending from the lid, the skirt including a line of weakness facilitating a manual tear of the skirt. The threadless cap further comprises a tear stop at a location intersecting a line of tear propagating as a result of a manual pull applied on the skirt, the tear stop preventing the line of tear to propagate beyond the tear stop. The line of weakness may include a portion extending across the tension ring to reduce a retaining force exerted by the tension ring on the neck of the bottle when a tear line propagating as a result of a manual pull applied on the skirt extends across the tension ring. Also, provided is a closure system that includes such a threadless cap and a protective sheath for application on the cap.
