[Wide Compatibility] : Expansion tank radiator cap is compatible with Porsche 996 Carrera (1997-2008), 996 turbo (2000-2005), 997 Carrera (2004-2012), 997 turbo (2006-2012), 986 Boxster (1999-2016), 987 Boxster (2004-2012), 987 Cayman (2004-2012), 981 Cayman (2013-2023) [OE Number]: The reference number of the expansion water tank cap is 171121321D, 443121321, 99610644700. [Protection Function]: Helps to prevent the water in the fluid reservoir overflow, ensure your driving safety. [Professional & Good Replacement]: Engineered to provide a tight seal for your vehicle's expansion tank, easy to installation. [High Quality]: Expansion water tank cap made of plastic material, it is corrosion resistant, against fading, not easily damaged, long lasting and.