A waste gas interface device must be used to reduce negative pressure (vacuum) if you are using central medical suction as a gas scavenger system. By balancing pressures between the anesthesia machine and the active evacuation, this device eliminates the possibility of having a "light" patient due to excess negative pressure. Model A629 with a flowmeter eliminates the need for a separate vacuum regulator when using medical suction. Includes 20 feet of 22 mm clear tubing, 4 feet of 19 mm tubing, and mounting hardware. 5 year warranty.