All Rebecca Hearth Jewellery pieces use standard Australian sizing for rings and chain measurement. A general size has been calculated for small medium and large where stated. Any custom sizing must be stated at the time of order. Most rings are able to be ordered in a custom size. Not all rings are able to be resized should they be ordered incorrectly. If this service is required a fee will apply. For all high value rings (or whenever possible) we recommend being sized professionally to prevent any issues with pieces being unable to be resized. We offer this service free of charge if you are able to visit for a consultation, otherwise a ring sizer can be purchased, contact info@rebeccahearthjewellery to order a ring sizer.