Astro Pneumatic No. 23 7858523 Radiator Test Cap (Late Model Audi, VW, Porsche)The Astro Pneumatic No. 23 7858523 Radiator Test Cap (Late Model Audi, VW, Porsche) allows easy testing for leakage in radiator system and quick change of coolant. Unit is suitable for late model Audi, Volkswagen & Porsche vehicles. The Astro Pneumatic No. 23 7858523 Radiator Test Cap (Late Model Audi, VW, Porsche) works with the 78585 Astro Pneumatic Universal Radiator Pressure Tester & Vacuum Type Cooling System Kit.