This coolant expansion tank with cap is designed for use with specific models including the 328d, 328i, 335i, 435i, M2, and M235i equipped with 2.0L and 3.0L engines.It is compatible with 17137642160 and functions to manage coolant thermal expansion while maintaining proper cooling system pressure.The included reservoir cap is engineered to provide a secure seal to help prevent leaks during normal engine.This component supports the overflow recovery system and aids in engine temperature regulation.