The shell is an operculum of a seashell, also called a shiva shell. The operculum is like a foot and serves as a sort of trapdoor to close the mouth of the shell when the soft part of the animal is retracted. It is found on beaches throughout the pacific, no live shell are used to make the bracelets.
Shells come on a silver filled bangle. The bangle does not open so much slide over your hand. It's best to measure the widest part of your hand.
oval shape - 3/4"dia
square shape - 1/2"x1/2"
rectangle shape - 1/2x 3/8"
Made in Hawaii