Packing list:Total 3 Kits. Each Model has 1 Kit Advantages: 1.Use one hand to fix, save time 2.Double spring system: optimal separation force to prevent ring deformation 3.High temperature and high pressure plastic head: greatly increase the service life of the product 4.Anatomical shape: perfectly adapted to tooth morphology FDA STATEMENT The sale of this item may be subject to regulation by the U.S. Food and Drug Administration and state and local regulatory agencies. If so, you can bid on this item only if you are an authorized purchaser. If the item is subject to FDA regulation, I will verify your status as an authorized purchaser of this item before shipping of the item.