Review on AQUACREST Inline Water Filter: The Ultimate Solution for Car Washing, Window & Yard Cleaning - Say Goodbye to Hard Water Spots! Softened Water with Upgraded Formula! Pack of 2 by Jeffrey Shatzel

I've been using it for a few months, I think it's doing a good job. I'm in a heavy water area and have a medium dark car (not black, more of a medium metallic blue). The water flow doesn't seem to be impeded, which I find a bit of a shame. However, I can dry my car without stains - or at least +95%. The secondary purpose of the filter is to clean the water before it enters my electric pressure washer. So for this use case I think it works as advertised. You still need to dry your car in time - most importantly, don't wash it in direct sunlight and use a quality car shampoo.