This piece is used with the 5/8 x 5/8 x 5/8 heater core hose tee.

It is used to reduce the flow of coolant to the rear heater core and replace the NLA fitted VW hose with 5/8 heater hose while still keeping all coolant pressure in the Vanagon proper and happy.

Since you are eliminating the now obsolete tapered rear heater core hoses with straight 5/8th heater hose, you will need to install the aluminum reducer (supplied) in the hose that goes to the rear heater control valve in order to assure that the front heater core gets the proper flow of coolant.

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Ref ID: VCHTRCOREREDUCER

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