HOW TO KNOW WHAT SIZE RING TO BUY
All ring sizes can be adjusted for a perfect fit - but it's useful to get some idea of your partner's ring size beforehand ( especially if it's a surprise purchase and you want it to fit first time ).
So download and print PDF below ( don't use print screen; it'll come out the wrong size ). Then quietly lay one of his or hers rings on top of the guide to se which size is the closest.
Remember to put it in the bin afterwards, leaving this lying around can give the game away.
IF YOU'RE LOOKING FROM OVERSEAS:
RING SIZE INTERNATIONAL CONVERSION TABLE