I would give 5 stars, as my first 4 rides have been really good - love the different speeds, great range, everything working well. However, installation was much more painful than it should have been. The magnetic ring that fits the crank was the wrong size in spite of my providing my cycle's details - I should have had the universal disc rather than the standard one. I contacted customer service and had to push for a replacement. Then, for some reason, the same standard disc was sent to me twice more. In the end, I gave up, and cut down the inside of the standard disc so that it fits. Not ideal, but I have ended up with a product that works really well.