The VW part number 1JA is a Genuine Volkswagen/Audi/Seat/Skoda Fuel Water Separator Filter designed for 1.9L and 2.0L diesel engines, typically from 1994–2008. This inline filter removes water and contaminants from fuel to protect the fuel system and engine. It is commonly used on VW Beetle, Golf, Jetta, and Passat models.