The Nissens AC Expansion Valve - 999358 is a component of a vehicle's air conditioning system. It is responsible for regulating the flow of refrigerant into the evaporator, which helps to cool the air inside the vehicle. This expansion valve is designed to fit specific makes and models of vehicles and is made with high-quality materials for durability and efficient performance. It is an essential part of the overall AC system and plays a crucial role in maintaining a comfortable temperature inside the vehicle.