I'm surprised. I've used them for several years, and had great success. So much so that I've recommended them to many other people who also had good results. Generally when it works, you don't pass a "stone" but just small black granules of dissolved stone,
so possibly you were to the point that the stone was already going to pass.
I had 17 kidney stones on one side and 21 on the other in the scan. At about 2 weeks of filtering with a paper cone each time to be sure, I passed what looked like black sandy granules. After 3 weeks on Uriflow, I went back for another scan and NONE were found. It may not work for everyone, I don't know, but it definitely works very well for many of us.