The Chevron Pneumatic Tubing 1063636 a 500-foot roll of 5/32-inch black twin tubing, is the workhorse of your HVAC system's pneumatic controls. Pressurized air is sent by this air-powered tube to run various parts of your building, such as actuators, dampers, and thermostats, controlling pressure, temperature, and airflow. https://www.partshnc.com/1063636-chevron-pneumatic-tubing-532-twin-tubingblack500ft