The Omron mesh cap is made to be used with the Omron Micro Air U100 portable nebulizer system and attaches to the medication bottle. The mesh cap generates the mist that you inhale, without it, the system will not work properly. Mesh caps are maintenance items and do not carry any warranty from Omron Healthcare. The mesh cap should be replaced at least every year, or anytime you notice you treatment begin to slow down. Properly maintaining your mesh caps will prolong the life of your nebulizer.