Ideal for every boater who has ever forgotten to put in the plug! This patented one-way safety plug lets water out of your bilge but not back in. The One-Way Safety Plug comes with an exclusive garboard plug with a handle that allows the plug to be tightened and loosened with a wrench, screwdriver, or even a nail. 1/2" NPT female plug. Safety plug: 2" dia. x 1.5"D with a 1" dia. opening.