The structure of the ePTFE porous membrane is water & dust & temperature proof which is ideal for relieving air pressure & moisture caused by temperature difference between day and night. Furthermore, the membrane is protected by a small & smart designed AVC Protective Vent Plug which is weather-resistant and flame-retardant suitable for outdoor electric device application (Telecommunication, PV or Lighting...ect ) and enable them to keep out water and dust and still allow product to breathe with outside environmental air to longer product life.