The best! I've been using this product for years in both my bathrooms. First time I used it I followed the instructions and drained the bowl. After letting it sit about 24 hours with a little scrubbing while waiting, both bowls came out in mint condition. Since then I don't bother to drain the bowls, just squirt the cleaner around under the rim and let it sit 12 - 16 hours. I do this every 10 days (results will probably depend on the mineral content etc. of your water.) No more brushing at all!