my husband's ring finger was measured at 10.5 in the store and I read several reviews that you should go a size up--WRONG! we ended up having to exchange 2 times because the rings were too loose. we originally had the 8mm but he preferred something a little thinner. this 6mm ring is the perfect size and fits perfectly (went down .5 in size). he works and works out with it on and it never scratches or dents. tungsten carbide is pretty amazing...