Capped Pendant with metal fittings is approximately 5.5cm. Various crystal assortments in Rose Quartz, Green Aventurine, Sunstone, Amethyst, Lapis Lazuli - Crystal will be depending on stock and availability on purchase.
Om and Aum are the same thing; it's just written two different ways. the sound of "Aum" - the slow, calming chant many associate with the word, is the sound that was made when all of creation came into existence the essence of the universe and the source of all manifest existence.
The "Om" represents the four divine states of Brahman - metta (loving kindness), karuna (compassion), mudita (sympathetic joy), and upekkha (equanimity). Brahman is actually a core belief system in both Hinduism and Buddhism, both of which use Om regularly in their daily life.