This idler pulley is found on the upper left side of the engine, below the A/C compressor on Discovery II and P38 RR. The pulley was originally made from plastic. After some time, the plastic pulley would become deformed, causing excessive noise or chirping from contact with the serpentine belt. LR began to replace the plastic pulley with this heavy-duty metal unit. Fits all Discovery II models and all P38 RR models from 2000 to 2002. Also fits some late 1999 model year P38 RR with the Bosch engine management system. (If your RR has two exhaust pipes, this will fit.)