Frame" Size" Knob for all opening ports - Black Only 1/4 - 20 Hole" Designed with drain molded on inside of spigot. Promotes drainage without angle cuts in hull. Allow for thru-bolting. Seats tightly against gasket and lens omitting internal water retention ledge. No water fall when opening after a rain. Ideal for mounting where installation is within 15 of vertical or where no drain is necessary. Patented. All self-drain ports have a White body and a clear window. 1" spigot.