The flow meter is silent wen in operation and from what I can tell, does not introduce any noticeable restriction in flow. I am pumping a cooling fluid mixture through it that is similar to common automotive antifreeze so its slightly thicker than water.
Using a CPX Pro (jingway 1200) pump from Dangerden.com I am getting an output of about 400lph on average which is consistent with testing from other independent testing labs.
I have tested this setup on another pump (Thermaltake 500lph) and the results from it are also consistent with other results I have seen.
I really hope some of you use this in your projects. If you do please email me (charles gantt at themakersworkbench dot com) a link to your project.