The M control lends itself ideally to conditions requiring a great deal of stability and accuracy. Designed for settings from 0.01 to 0.1 in, the Field M Control is recommended for oil or coal-fired residential heating applications. The type M features an infinitely variable screw adjustment, permitting an extremely fine instrument setting. The M employs side wings to control air direction with gate curvatures designed to compensate for differences in horizontal and vertical settings.