Sea-Dog Line These Hose Deck Fills feature a slotted cap which requires a key to open and close for extra security. Cap diameter 1-7/8", thread pitch 11-1/2 NPSM straight. Caps are color-coded for easy deck fill identification, eliminating dangerous and potentially costly problems caused by misidentification. All fills and replacement caps (except waste) include attachment chain. Constructed of fiberglass filled injection molded nylon. These fills contain no metal and do not require grounding to the boat's electrical system.