The Autolite 216 spark plug is designed for some small engine applications such as the 616-720 Allis Chalmers Garden Tractors equipped with the CCK Onan twin cylinder engines 19.5HP engines. The 216 will also fit some early Onan "BF" series engines needing a 14mm thread and 7/16" reach. This particular plug has a gasket ring for sealing on the bottom. A 13/16" hex socket size and non resistor style design plug.   This plug will also fit the Kohler "K" series engines such as the K241, K301, K321, and K341 single cylinder engines.