The Bendix+ QR-L is a quick release valve. Its purpose is to -speed up- the release of air from air lines and devices it serves. Although primarily intended to enhance air system performance by rapidly exhausting supply or control air pressure from vehicle airlines, it can be used in a variety of different applications. It is uniquely suitable as an air system performance enhancement due to its 0 psi crack and differential pressure. Supply and delivery pressure is the same throughout the air pressure range.