The Pro water bypass fittings increase engine performance by diverting water from the cylinder head to the bypass fitting, rather than forcing all of the water through the exhaust system, thus drying out the exhaust. Hose Diameter: 1/2" Inch Thread Length: 1/2" Inch Nut Width: 1-1/8" Inch NOTE: Install with 3/4" Inch Drill Bit. Fits a 1/2" inner diameter water line and requires a 3/4" mounting hole drilled through the hull. If you are unsure if this is the correct size, then measure the inner diameter of the waterline! Jetski Waverunner 45-degree 3/8" water bypass pisser