Worked GREAT on the toilet bowl. FAIL on hard pool calcium.
Living with Florida water can leave a permanent ring around the water bowl in the toilet. I had tried everything to remove this unsightly ring on the bowl, with zero success, until I bought these pumice stones. These worked incredibly well. I also wanted to use one of these pumice stones for the calcium buildup in my pool. It was a complete fail. These pumice stones practically disintegrated. Couldn't stay together long enough to remove any calcium buildup. So that was disappointing.<br />Depending on the your project this could be the perfect product. The jury is still out on cracked heels.
Rating: 4 stars