This is the hose that carries coolant from the cylinder head to the throttle body heater unit on the M42 engine in the 1990-1991 E30 318i and 318is sedan/coupe, as well as the 1990, 1991, 1992, and 1993 318ic convertible.
This is a Genuine BMW part, so you can be assured a perfect fit and a long lifetime.
BMW Fitments:
3 Series
E30 (84-91) > 318i
E30 (84-91) > 318is