The ring and cap method of sealing these jars is not necessarily airtight on its own. That method was designed for the canning process. During that process the air is sucked out of the jar and the rubber-lined lid is sealed, airtight, against the lip of the jar. The ring is just there to hold it in place during that process.
These rings and lids won't necessarily keep your jars airtight on their own. For that, it's better to use these (admittedly less cute) plastic sealing lids. You can get them in hardware stores and on Amazon.com
• Ball 36010 regular canning jar plastic storage caps, $2.99 for 8 at Amazon through Goodman's