The 14-BP is a calibrated bypass. It has a 3mm diameter orifice and it is designed to be used with 1/4" ID hose. It is used where a certain water flow pattern is needed without the need to use a 3/8" hose. An example is the back cylinder area of the cylinder head where only one cooling line is used to cool the engine and overflow is not needed. Another example is on triple cylinder engines where a small bypass is needed to exit off the middle cylinder.