Automatic water top-off device compatible with 6mm and 5mm tank walls. It is recommended to use a uniformly shaped iced tea bottle (possesses superior rigidity, less prone to deformation; cola bottles may fail over time due to deformation and cease automatic water replenishment). A 24*2.4 sealing ring is suggested. The outlet and inlet outer diameter is 6.1mm (an Yili fruit yogurt straw or a flexible tube is suitable).