This fitting is a metric fitting on one end and an AN male fitting on the other. This fitting is very popular. Applications include. All watercooled CHRA coolant lines on garret and older style precision turbo chargers from gt28r-gt35r. Some larger framed turbos use these as well, always consult the manufacturer out of this range. This is the same size as the coolant return fitting in the back of the block from the stock turbo on all mk4 1.8t engines and all longitudinal vw/audi 1.8t engines with internal waterpumps from 2001-2006.