CTS Turbo Audi B9/4M Billet Coolant Reservoir Cap

The CTS Turbo Billet Coolant Reservoir Cap replaces the factory plastic unit on B9 and 4M platform Audis with a precision-machined billet aluminium alternative. Designed specifically for 2016-2021 Q7, A4, S4, A5, S5 and SQ5 models, this cap delivers enhanced durability and improved sealing performance under engine bay heat cycling. The anodised finish resists corrosion whilst providing a refined appearance in the engine compartment. CNC-machined construction ensures precise thread engagement and consistent seal pressure, addressing common failure points of the standard plastic reservoir cap.