I was disappointed initially as the cartridge seemed to stop working in about a week. I tried experimenting with it and discovered that if you turn the cartridge all the way down that sometimes blocks the water from getting to the ports of the cartridge. The cartridge screws in and I tried not screwing it in all the way and it started working again. You don't have to back it off very much, but that seems to allow the water into the cartridge ports again. Its actually adjustable as to how much bluing you want in the water which affects how long it will last. I have hooked two of them in tandem, one has the bluing effect cartridge and the second one has the chlorine based cartridge. This way I get both good cleaning and the bluing effect that we like. Seems like this should be mentioned by the manufacturer in their instructions of how to install and use it.

Have always used the drop in tank tablet cleaners but decided to give this one a try.
Was fairly easy to set up and install although very much depends on the kind of system you have in your tank so research that first. I had to use a different hose for part of it because the one provided was just too short based on how I had to hang the system and where the connections were.
After figuring all that out which only took a few minutes everything worked perfectly. Some have said they smell chlorine a lot from this unit, I myself did not at first. After a few days you sometimes might catch a very slight hint of it for a second or two and that's it. Nothing horrible whatsoever. It works like a charm and kept the Bowl cleaner than anything else I had ever tried.
The only downside I can see from this, depending on your point of view, is the cost. You do have to replace the filter and it is fairly inexpensive but maybe not over time. As many have mentioned there is a way to alter the unit so that you can use much cheaper replacement tablets without having to get a whole new filter.
It is solely because of this reason that I give it 4 stars instead of 5.

I ordered this product for my office which would have usage similar to a residence. Product seemed to be well manufactured and a better design than others I have tried unfortunately it stopped the toilets from flushing, lots of flow and large amount of water in bowl with very dark blue color but no flush! After installing and then removing several times I came to the conclusion that it was definitely the Flush and Sparkle product causing the problem as I could hook the old overflow line up and the toilet would flush properly every time. I contacted Fluidmaster via chat and was advised that it could be related to the cartridge being old i.e. the blue cleaner was disintegrating too easily and blocking the flow. This seemed reasonable as the blue cleaning material was eroded away by a significant margin and when I removed it and flushed it out with water to the point of the cartridge being empty and reinstalled the empty cartridge the toilet would flush perfectly. They had me send photos of toilet tank with Fluidmaster fill valve and toilet brand info etc. it is an older regular flow toilet from the 80s so the CSR said the unit may not be compatible. They sent me a new package of refills at no cost but it created the same problem. I followed up and the chat CRS advised the system was apparently not compatible with my toilet and Fluidmaster fill valve? Based on my observations and the fact it works perfectly when the cartridge is empty makes me believe the flow is being disrupted/blocked due to the soft cleaning material being dispensed at too high of a rate which is possibly impacted by the longer fill time of the older toilet. I questioned if using the chlorine refill would possibly work but they did not recommend it given the issue I was having. I may try using chlorine tablets in the empty cartridge just to see if my theory is accurate.

I've installed these in all six toilets in my home and they are a great idea. I've been using this for about 4-5 years. This device circulates bleach product into the toilet bowl after every flush where it is needed to prevent staining such as water lines from calcium build up. However the chlorine water is restricted to the bowl, not the tank. If chlorine is in the tank it will erode away the "flapper" and foam seal which separates the tank from the bowl, requiring more expensive repairs. This product solves that problem with no drawbacks and don't look unsightly like the clamp-on bars of chlorine that are permanently inside the bowl.

I had a hard time finding this item as some hardware stores do not carry them. I purchased for our Florida condo and I have been using these in our house and love the way they work. They clean the bowl with each flush as it hooks into the water line, each flush pushes water through unit and adds bleach to clean bowl. We still clean bowl as needed about 1 time per week and this helps it stay cleaner longer. The condo gets less use so I cannot wait to how well it works there. The area has harder water so this may help with rings inside bowl. They last about 3-4 months each, but it does depend on how often it is used.