1000. Grommet. A rubber ring with a hole in the center which provides protection through which Heater Core Tube related components pass through. A/C Line O-Ring. A/C Refrigerant Line Grommet. HVAC Heater Core Seal. (A/C) Line O - Ring. (A/C) Refrigerant Line. Core Seal. Hose Outlet Tube. Included with: Evaporator assembly.