The Rein Expansion Tank (E60) - EPT0128 is a replacement part for a vehicle's cooling system. It is designed to hold excess coolant and maintain proper pressure in the system. This expansion tank is specifically made for the BMW E60 model and is a direct fit replacement for the original tank. It is made with high-quality materials and is built to meet or exceed OEM specifications. This product is essential for maintaining the proper functioning of a vehicle's cooling system.