These style of beads are made by the Krobo (pronounced Crow- bow)tribe of the eastern region of Ghana, they are made of a combination of clay and glass and baked in the special ovens. They are hand painted and arranged on elastic style bands so they can be worn on wrist, pushed up to the forearm or even around ones ankles.
I am sure similar beads styles are worn all over West Africa, as we tend to share a lot of artistic styles (and Jollof rice). In Ghana they are usually worn for special occasions like engagement ceremonies, weddings, baby outdoorings, and funeral. They compliment traditional ankara patterns and wax prints perfectly, but I personally love to add them to western style clothing for an extra pop of color!