This is one of the most important parts of the lamp system. As its name implies it is used for covering the stone to stop the lamp working. It should also always be put on the lamp whenever the lamp is not actually working. If you do not cover the stone fully when the lamp is not working, any oil in the lamp will continue to be fed to the stone where it will evaporate leaving concentrated fragrance in your stone. This is the most common way that the stone stops working as the micro-pores in the stone become blocked with fragrance. Always cover the stone fully with the snuffer cap when the lamp is not in use.