TWIN EFFECT1935-40.1935-41.1937-1948.1937-48.1947-54.1948-1952.1949-1954.1949-54.1953-56.1955-59.1990s. There are videos available on YouTube that show how to set up, adjust and use the pedal. It has heel switches on each side that allow for very quick transitions between single and double action play.