If you are unable to determine the size of the finger you wish to purchase a ring for, we can send you this Ring Sizing Band with a $5 coupon code to use on your next purchase!
 
Simply slide the band on the desired finger, pull until its a comfortable fit, and look to see the which size the arrow is pointing to on the band. 
 
Make sure the band slide on and off of your finger.  You do not want it to be too tight!