Genuine OEM Audi timing chain guide rail, part number 05A109517B. This rail is a vital component of the timing drive system, designed to guide the timing chain and maintain proper tension to prevent chain slap or skipping. It is manufactured from high-wear-resistant polymer to minimize friction and noise during high-speed engine operation. Genuine OEM guide rails are essential to ensure the correct material composition and structural integrity required to prevent catastrophic engine timing failure.