The First Company CP81-51 0.051" Orifice Piston is a refrigerant metering component designed to regulate refrigerant flow through compatible HVAC systems. Its precisely sized orifice restricts and meters liquid refrigerant entering the evaporator, helping maintain the appropriate flow rate for efficient heat transfer. This piston is used in compatible air conditioning and heat pump in... https://www.partshnc.com/first-company-cp81-51-orifice-piston-051