plugged black drains

I was looking for some stuff on amazon that was rv related and I came across an item that you place on the dump tube and you hook up a garden hose and back flush a tank if you have a slow or blocked drain tube. being a few days ago so don't remember how much it was, didn't seem like much at the time. it was made by camco. there have been posts on the forum in the past about plugged drains and what do I do now questions. I think this would work well in that situation.