Ring sizes are in US sizes. Please check US to AUS ring conversion charts to check for Australian sizes. As a guide, rings are displayed as petite, small, medium and large. Please be aware that if a particular style ring has a wide band. then these styles will fit more snug/tight.
If unsure of your size, it is best to go to a jewellery shop to get your ring size measurement. Or shop with more confidence and avoid exchanges with Ring Sizers. Check them out here.
If sizes are not displaying in drop down menu, then this means that it is sold out and not available.