Please note, bending these bangles too much can cause them to fatigue and can occasionally cause breakage. Please ensure you select a size that will sit comfortably on your wrist without requiring continual tension on the metal. After ensuring it is closed to a shape that fits comfortably, you should take it off by slipping it off the side of your wrist rather than bending it. Eventually, the bangle will take on a shape unique to your wrist as a result of everyday wear.
If you are unsure of your bangle size, a good way to measure is by taking a piece of string and measuring the circumference just below your wrist bone. Lay the string along a ruler. Then subtract to allow for some thickness of the wrist. For almost everyone, subtracting 2.5cm will give you a good measurement for a bangle.