Orion Motor Tech Oxygen Sensor O2 Downstream for BMW 323i 325i 328i 330i 525i 530i X3 X5 Z3 Z4 Compatible with 11781433940, 234-4683, 2344683, SG899, ES10857,15109 Designed to detect the amount of oxygen in the exhaust system Direct fit Fast-acting heater optimizes sensor operation Coated threads for easy installation