The Flow Control Valve provides improved throttle response and muchquicker starts by drying out your waterbox at low rpm and idle speeds.Tests have shown an average acceleration improvement of 10 feet over anon-equipped model in the first 50 feet. The Flow Control Valve allowsunrestricted water flow to the Stinger for better top speed.Yet it controlsthe amount of water at low speeds for better response. It also allows foran easier tuning of the Carburetors. It does not interfere with normalengine or exhaust pipe cooling and is compatible with all electronic waterinjection systems. Race Legal for All Classes.Two Models are available.Both are adjustable. The Standard Flow Control Valve is preset at 3.5p.s.i. and is adjusted by adding the supplied stainless steel shims toincrease the spring tension. The Pro-Series is externally adjustable byturning the outer housing by hand. Pressure can be tested with pop offgauge. All PWC w/OEM or aftermarket exhaust systems (exceptYamaha�s w/OEM exhaust)