This bangle requires an internal core support. We suggest using a core with a 2 1/2–3-in. (6.4–7.6 cm) inside diameter, or any other diameter that's large enough to fit over the wides part of your hand. You can use a plain purchased metal bangle as well. Also, see "DIY vinyl tubing core" on p. 3 to learn how to make your own core from supplies available at local hardware and aquarium stores.