Each pack includes 10 gemstone rollerball inserts, crafted with genuine Black Obsidian, and designed to fit standard 5ml and 10ml essential oil roller bottles (approximately 9.7mm inner diameter bottle neck). Rollerballs are smoothly polished for even oil release. All Essential Wellness - Body, Mind, Spirit products are cleansed, then Reiki-enhanced with love and healing intentions, making them a thoughtful and meaningful addition to your wellness product line. Beautifully designed gemstone information cards explaining benefits and properties, as well as an aligned mantra, are available separately BLACK OBSIDIAN ♥ Purification ♥ Transformation ♥ Fulfillment ♥ Metamorphoses ♥ Manifestation ♥ Practicality ♥ Psychic ability