When the coolant pressure in the radiators exceeds the set value of the pressure cap, the coolant is sealed through the pressure cap and flows into the radiator coolant overflow tanks through the overflow tube. The tightly sealed cap, fully TIG welded and equipped with an O-ring at the threads, allows the coolant tank to maintain a nice closed environment and prevents coolant leakage. Level indicator of the tanks for easy reading of the liquid level. The switchable inlet/outlet and the level indicator can be placed on the right or left side of the aluminum tank. Made of high quality aluminum alloy with anodized surface, sturdy and with nice durability, corrosion resistant and not easy to rust. Easy to install and use, suitable for most vehicles. Bottom with electromagnetic drain plug design, easy to discharge and clean.