Derale 15782 Thermostatic Universal Engine Sandwich Adaptor 3/4″-16, 13/16″-16, 18×1.5mm, 20×1.5mm + 22×1.5mm. 2-3/4″, 3-1/2″ O-Ring Diam. 1-3/4″ or 2-1/8″ thick. 3/8″Npt Ports