Precision Works Radiator Inline Filler NeckPrecision Works Radiator Inline Filler Neck This filler neck is an awesome upgrade for our tucked radiator and compact radiator line of products, as it allows you to add this filler neck to the top port, providing easy access to fill up coolant, add temp sensor, fan switch, overflow tank, etc. One end of the fitting is 16AN Other end is 1. 38" hose connection Commonly used in Honda, Toyota, and Subaru Inlet and outlet uses 20AN female ORB threads Uses