One size will fit most, as these are a CUFF style bracelet so they are opened ended, not a round closed circle bangle. It measures about 6" long with about a one inch gap that can be pinched tighter or pulled apart to fit perfectly. Measurements-Clare: 4.5mmJeannie: 5mmFarrah: 4mmRobin: 4mmMandy: 6.5mmHope: 5.5mmBella: 5mmAngie: 8mm