Perko Vented Flip Top Cap f/Fills with 1-1/2" Hose. Black Polymer. Easily Mounts Directly on Gunnel with Removing Fill Body. Includes Metallic Inserts for Gas, Diesel or Water Fills. Integral Tank Vent with Flame Arrestor. No Deck Plate Key or Ground Wire Required. Flip Top Cap. Technical Information. Requires 5-1/4" Diameter. Mounting Surface Screw Size: #8