Upper Timing ChainThe timing chain in any vehicle can begin to stretch and rattle over time. BMW says it is a 'lifetime part', but we recommend replacing them on very high mileage engines when installing a new vanos. IWIS brand chains are top quality and offer 2 versions, Standard and Racing. The standard chain is fine for all applications, while the Racing chain has slightly thicker link plates that resist stretching. Fits all E36, E39, Z4 with M50 M52 S50 S52