These are a modern modification of the traditional bracelets which were worn by both men and women for protective purposes, as well as personal adornment. We had the Malian artisans who make the bracelets make them a little larger for some to be worn as anklets. The leather of which these bracelets are made is goatskin. These are considered in Mali to be of  medicinal or spiritual value which defend the wearer from whatever he or she may consider to be threatening to them. Cowrie shells, prior to European occupation, were currency and so still reflect their former significance. The clasp for each is the traditional ball and loop style. 

This bracelet may be large enough for some people to wear as an anklet.

These cowrie shells are the real thing, vintage shells that for centuries were popular currency in West Africa.

The sizes do vary but most are approximately 3" (8 cm) in internal diameter.