The product is a genuine Toyota heater inverter coolant reservoir tank designed for the 2004-2009 Toyota Prius. Manufactured in Japan, this radiator component is specifically located in the engine compartment of the vehicle. It comes with the OE/OEM part number 1666021011 and is also known by the manufacturer part numbers 16660-21011 and STK528727. This high-quality part ensures proper functioning of the vehicle's cooling system, making it a crucial component for maintaining the optimal performance of the Toyota Prius.