This fitting is a metric fitting on one end and an AN male fitting on the other. This fitting is very popular. Applications include. Oil feed line fittings that thread into the oil filter housing on the mk4 and late audi/vw 2001+ internal waterpump engines and in the mk5 2.0t fsi motors in the back of the engine (left side) where the oil feed fitting is located on that car. This fitting is what you need for your aftermarket turbo kit or if you are piecing together your own kit with a 4 an line which is recommended for all ball bearing and now recommended for journal bearing turbos.