Anytime I have ever used these they fell apart and left chunks of cleaner along the rim. They were more trouble than they were worth.

You're right about the ones with bleach eating away at the rubber parts. I learned that the hard way. My plumber simply recommended avoiding any cleaner that you leave in the tank, even the ones that don't have bleach.

We had one ... not sure if it was bleach or not ... that got stuck in a funny position so that the toilet would not flush well, and drain like it should. We thought something was stuck in the toilet and plunged like crazy, then we tried changing the flap, plunged some more, bought another flap ... a month or so later called the plumber, who found the silly half dissolved cleaner stuck in the tank. So ... no more. I prefer the gel that you can stick into the side of the toilet bowl. Comes in a long stick and you push out one gel "portion" at a time. That worked and smelled great.