The Perko Flush Pro™ Valve offers one of the easiest to use flushing systems available for inboard engines. Simply unscrew the Flush Pro™ cap, connect a standard garden hose, turn on the water and start your engine. The Flush Pro™ valve automatically pulls fresh water into the boat's cooling system - even if the boat is in the water - flushing out the entire cooling system with fresh water. When done, shut off the engine, turn off & disconnect the hose and replace the Flush Pro™ cap. Your engine is flushed. Flush Pro™ also makes winterizing easy. Simply close your seacock after the system is drained, take off the Flush Pro™ cap & drop the 5/8" winterizing fitting into the Flush Pro™ valve. Insert one end of a 5/8" tube into the fitting and the other end into your antifreeze. Start your engine & run until the proper amount of antifreeze is sucked into the engine. Remove the winterizing fitting, replace the cap on the Flush Pro™ valve & you're ready for below-freezing temperatures. Perko Flush Pro Valve Features Easy to use Makes winterizing easier Fits 1-1/4" hose Valve