Genuine OEM Audi slide rail, part number 059109509D. This rail is a critical component of the timing chain assembly, providing a low-friction surface for the chain to travel along while maintaining correct tension. It is located within the engine timing cover assembly. Genuine OEM slide rails are manufactured with high-strength, wear-resistant materials to withstand constant thermal cycling and mechanical stress, ensuring precise valve timing and preventing chain slap or premature engine wear.