Measure the inner diameter of a ring you own, and send me the exact measurement (preferably in cm and mm). Look at the image below to see which measurement I need. When you measure the ring, make sure you place your ruler across the middle of the ring (as if you were cutting it in half), and don't measure the thickness of the metal. The result will be something like 1.8 cm.
Most of my rings are open at the back and can be made a full size larger, so don't worry if the measurement is not perfect. I just need to have your approximate size.