Mishimoto 1.1 Bar Rated 99-15 Ford F-250/F-350/F-450/F-550 Super Duty Overflow Reservoir CapGetting the most out of your performance parts comes down to the details. When faced with hard driving conditions, a vehicle's cooling system becomes highly pressurized. Factory caps are not equipped to handle long term use and often lose pressure, in turn reducing the potential coolant boiling point and boiling the coolant. The Mishimoto 1. 1 Bar Overflow Reservoir Cap will keep coolant where it needs to be, flowing within the system. This Part Fits: