What's in a name - is there a difference?
Often but not exclusively worn by women who are pregnant a Harmony Ball or Bola Necklace or Angel Caller or Bola de Grossesse or Harmony Necklace or Pregnancy Necklace is a chiming necklace pendant said to provide harmony between the mother and her unborn child - refer this detailed authoritative article on the 'Benefits of wearing a Harmony Ball during and after the pregnancy' which highlights the real benefit and dispels the myths.
Whatever name it is called, the buyer should be aware that there are two types of Harmony Balls, Bola Necklaces, Angel Callers etc - 'Real' and 'Copies' - 'Real' ones are Hand Made primarily of Sterling Silver - 'Copies' are mass produced in China and are 'only Plated silver' - only one will ever last to be a 'Keepsake' to hand on to your Daughter.
So with so many names, is there a difference between them? - basically not. The Harmony Ball originates from Bali, Indonesia whilst the Bola Necklace or Angel Caller or Bola de Grossesse are of Mexican origin - both cultures having used the chiming ball for wearing by expecting mothers, among other uses (for example the ancient chiming Druid Ball was worn in Battle by Scottish warriors).
The only real difference, aside from name and aside from the critically important 'Real' and 'Copies', is some variations in design, primarily culturally evolved variations of a theme.This article 'What is a Harmony Ball?' gives more insight into the history and cultural aspects of these necklaces, also called simply a Pregnancy Necklace
Sterling Silver Harmony Balls shown in the images in this post are available from https://www.harmonyballpendant.com/ - use the discount coupon code on the right to get a bargain.