... balance plug: 1.ISO9001,14001 certified, 2.waterproof grade: IP67, 3.long life time, Materil: ePTFE ePTFE pressure balance plug :material ... plug1. Grade: IP67.2.waterproof,but air can go through, 3.equalize the pressure inside&outside. Main advantages of ePTFE pressure ... , cleanser and other low-surface tension liquid;3, avoids water vapor or harmful battery gas being saved inside of the device case ...