Sea Dog Replacement Deck Fill Water Cap- BlueFeatures: Fits Sea Dog brand 1-1/2" Deck Fills; Cap molded from Fiberglass Filled Nylon; The cap threads are 1-1/4" - 11-1/2 NPSM - Straight; Gas, diesel and water caps include attachment chains; Built-in key for easy cap removal; Caps are molded in special colors to help prevent the dangerous and costly problems caused by placing fuel in water or waste tanks or vice-versa;