We designed and manufactured this adapter fitting for our Radiator and Inline Filler Neck. They're both designed using a -20AN O-Ring Boss (ORB) connection. This allowed both products to be modular in what Inlet/Outlet type can be used.
This particular one is machined from 6061 Aluminum and left in it's raw aluminum form to be fabricated easily. It is made to adapt -20AN ORB Female parts to a 1.25" ID aluminum opening (factory water neck, thermostat housing, etc.)
We also make the following #20AN ORB Male Adapters:Chase Bays -20AN ORB to -16AN Adapter
Chase Bays -20AN ORB to -20AN Aluminum Adapter
Chase Bays -20AN ORB to 35mm / 1.38" Push-On Hose Adapter
Chase Bays -20AN ORB to 38mm / 1.5" Push-On Hose Adapter