Please Note: This is a smart ring sizing kit. Since the size of a Lynx smart ring differs from standard jewelry ring sizes, please purchase this 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