You can expect up to a 20% increase in thrust from this pump tuning kit. Get the most from your pump by taking out the additive effect of stacked tollerences inherent in all assemblies. Each of the components in your pump assembly have a +/- tollerence from each respective manufacturing process. A pumps performance is increased by minimizing the gap between the pump wall and the impeller blades. This kit allows you to test a sequesnce of three wear rings that are all .5mm increments thicker than the previous, with the first being .5mm thicker than your stock wear ring. You chose the wear ring that allows the smallest gap without the impeller touching the ring and your pump is tuned! It is that simple and you will notice the difference - guaranteed! ***Important*** You will need to install a PBBR kit or block off your stock bilge in order to realize the increased thrust potential of this upgrade.