Mechanical alternator belt drive tensioner assembly for the BMW M50/M52/S50/S52 straight-six. Tensions the serpentine belt that drives the water pump, alternator and power steering pump, and includes the roller; a worn tensioner allows belt slip/squeal and can lead to belt failure or reduced alternator/water-pump output.

Fitment: BMW E36 3 Series (325i/323i/328i and ic/is variants) with M50/M52 engines, and the E36 M3/Z3 M with S50/S52 (confirm exact engine at checkout).