This is the 20M Complete Carb used on the O. S. Max .37 SZ-H Engine. OSMG1945. FEATURES: Genuine OS Engines replacement parts INCLUDES: One completely assembled carb Two 3.5x5mm carb retaining screws OSMG3836 One carb gasket (O-ring) OSMG6220 REQUIRES: Installing on crankcase using the included retaining screws & gasket SPECS: Length: 23mm Width: 75.5mm (including throttle arm and needle valve) Height: 34.5mm Diameter: 15mm OD of intake (throat) 12.6mm ID of intake at widest point (top) 8.06mm ID of intake at narrowest point (bottom) 8.2 to 10.2mm (oblong) ID of neck at widest point (bottom) 8.1mm ID of neck at narrowest point (top) The neck is the part that inserts into the crankcase tjt 020205 ir/jxs