1J0121619A is a radiator coolant flange compatible with many Volkswagen, Audi, SEAT, and Skoda models, primarily those from the late 1990s through the mid-2000s. It is commonly used on vehicles with 1.8L and 2.0L engines

Beetle (1998–2010): Fits various trims, including the 1.8L, 1.9L TDI, and 2.0L engines

Beetle Cabrio (2003–2010): Fits some versions of the convertible model.
Bora (1999–2005): Compatible with both 1.8T and 2.0L versions.
Golf Mk4 (1999–2007): Used on many 1.8T, 1.9L TDI, and 2.0L engine variants.
Jetta Mk4 (1999–2009): Fits various trims with 1.8L, 1.9L TDI, and 2.0L engines. 
Compatible Audi models
A3 (1997–2006): Works with some versions of the first-generation A3, including certain diesel engines.
TT (1999–2006): Used on the Mk1 generation, specifically on the 1.8T and 1.8T Quattro