Replacement one piece stone & wick assembly made especially for Greenleaf Aroma Decor Diffusers. * If your stone will not light, the oil reservoir may be empty. Simply remove the wick assembly and refill with the proper diffuser oil. Replace the wick and allow to soak for at least 20 minutes. * If you experience difficulty lighting the stone, then it may be time to replace it. The stone & wick assembly should be replaced once a year or every 250 uses. Use only with Greenleaf diffuser oils, due to the precise oil formulation that enables trouble-free operation.