Bracelets: For cuffs, the small and medium will fit most women. The large will fit a lot of men and some bigger-boned women. The extra-large will fit most bigger guys. When in doubt, you can send me the inner height and width of a cuff that fits you. You can also use a tape measure or flexible ruler to give me the (tight) circumference of your wrist; I will figure out the rest.
Rings: We use US sizing. If you order the wrong size or your ring does not fit, I will make you a new one at no extra cost. The extra shipping costs will be your responsibility, though.
For bangles, small is 2 3/8" inner diameter, medium is 2 1/2" ID and large is 2 5/8" ID. If you have a bangle that fits, you can tell me its inner diameter and I can match that. Remember, a bangle has to fit over your hand (this does not apply to my hinged bangles).
Putting on cuff bracelets: In my 25 years of selling jewelry I have found that a lot of people don't know how to put on a cuff bracelet. It is easy once you know. First, put the cuff on an inch or two below the wrist bone. (I'm talking toward your elbow, where there is less bone and cartilage.) Jam the bottom leg of the bracelet into that little hollow spot underneath (where the radius and ulna separate) and curve the C of the bracelet over the top of your wrist and ta-da! A cuff bracelet can be bent a little once or twice, to get the opening right, but that's it. Bending a bracelet everyday will eventually make it brittle and it will crack. If it needs to be bent to get on or stay on then it is either too small or too big. Whew! I don't know if that helped, but at least I tried.