PERKO (DP ITEMS) 6001607 INC Cowl Vent Series cowl Ventilator 1312DP0CHR per ko cowl Ventilator Uses #8 screws, chrome-plated zinc, black plastic base. 3" duct threads into neck hose clamps not Required, Mouth opening: 8'' square, 5-3/4"lx4-3/8"wx2-5/8"H