According to Chinese philosophy the yin and yang represent light and shadow, complementary forces working together to create a beautiful balance. Share our Personalized Yin Yang Keychain for Couples with that special someone! Yin yang accessories increase not only positive energy but also good fortune and luck! Choose any color birthstone crystal stone you would like to put on each half of the couples keychains set along with any engraving of your choice. Choose a name, word, or date! Couples keychains are very popular and you know you want to get this set!