bought this to fix fuel drain back problem

R you sure it is draining back to the tank and not into the carb. easy way to tell is to mount a clear filter inline just before carb, make sure it is mounted higher than the carb inlet and tilted down slightly towards carb. if it drains. it is going in the carb. often the inlet fitting (with the needle and seat) gets over tighten and holds the float slightly open.
there is no reason for the fuel to drain back from carb if hoses are tight with no leaks and fuel pump is good. normally when I disconnect the line at the carb it is still pressurized.
hope that helps