Required to fit late model Audi, Porsche & VW cooling systems with threaded filler necksWorks With 12270 Stant Cooling System TesterThread specifications Metric: 48mm x 3.0Professional quality12016 threaded adapter is required to fit late model Audi, Porsche & VW cooling systems with threaded filler necks. Thread specifications :48 x 3 : i.e 3 threads per inch and 48 is in mm which converts to 1.89” .