This tool will enable you, the consumer, to know whether the fur boot opening meets your requirements or whether you need a custom made boot. The calf of your leg must be measured 9 inches from the ground.
If, when your mesurement is taken, it is either equal to or less than the standard calf measurement indicated beside your regular dress shoe size (not your running shoe size), your circulation should be good. Otherwise, you definitely require made-to-measure fur boots.