Heater core grommet. A rubber ring with a hole in the center which provides protection through which Heater Core related components pass through. A rubber ring with a hole in the center which provides protection through which the HVAC Case or a part of said component passes through. HVAC Case Seal. HVAC Heater Hose Grommet. Part included in AC & heater assembly. core. Hose. Seal. Unit. AC AND ASSEMBLY. Evaporator tube.