Since the size of a Lynx smart ring differs from standard jewelry ring sizes, please purchase a sizing kit to find your perfect size and then purchase the Lynx health smart ring. The sizing kit includes 8 ring sizers (sizes 6-13) and a quick-start guide for this measuing tool to help measure your ring size more accurately. | Renpho | | Smart Ring Health Tracker, Sleep Activity Monitor Long Battery No Subscription Titanium | | 2025) | Black | Best Buy