These are easy to use, and I put the enclosed reminder on the calendar so I'd know when two months was up. We have two male dogs, and we keep these rocks in each of their water buckets. The dogs don't seem to notice. BUT! Our lawns certainly noticed. Really, the rings and patches of dead grass are substantially reduced. I believe even the rocks don't help in spots where both dogs pee repeatedly. And it doesn't help peeing on bushes. Our lawn has improved drastically, so we keep using these and have for eight years. Wish the price were lower on multi-packs.