These are a modern modification of the traditional grigri amulet necklace which were worn by both men and women for protective purposes, as well as personal adornment. That is, this grigri necklace is considered to have medicinal or spiritual value which defends the wearer from whatever he or she may consider to be threatening to them. We had the Malian artisans who make these necklaces make them a longer for us for stylistic purposes. The leather is made from goatskin.  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. 

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 24" (61 cm) in circumference.