Standard Air Manifold.  Fits Weber Kettle, Weber Smokey Mountain, and many other pits.  Installs without tools.  Toggle nut passes into pit through air intake and wing nut is hand tightened to secure manifold against cooker.  Fits against flat or spherical surfaces.  It has an inside diameter of 5-3/8", an outside diameter of 6-1/2", and a depth of 2-3/4".