Air tank (Part 103210), designed as a small compressed air reservoir used in the air brake and pneumatic system on Capacity terminal tractors and yard trucks. It stores compressed air produced by the vehicle’s compressor so that the brake system and other air operated functions (e.g., trailer brake relay valves, air accessory controls) have a ready supply of air when needed. It connects between the air compressor and the various control valves and actuators in the pneumatic system.