This is the large coolant hose running from the water pump to the thermostat.
Fits all E30, E28, and E34 M20 engines.
BMW Fitments:
3 Series
E30 (84-91) > 325e
E30 (84-91) > 325es
E30 (84-91) > 325i
E30 (84-91) > 325is
E30 (84-91) > 325ix
5 Series
E28 (82-88) > 528e
5 Series
E34 (89-95) > 525i M20