This is such a great idea, and it works very well!
I fill this bag up once a week (it drains overnight and is usually low or empty the next day) and it waters slowly, so the water gets into the soil deep, rather than just running off (as it did when I tried to use a sprinkler to water the tree). It's easy to fill (just shove a hose in the red filler hole), and I have had no problems with the emitters (there are two of them on the underside) getting clogged or anything.
Within the first 10 days of using this bag, I noticed new growth on the tree (after two weeks of nothing since transplanting it), and it's been growing steadily ever since.
If you want a convenient, stress-free way to water a newly established tree, that will help it snap out of its newly-transplanted blues, this is a great solution. I'll probably keep using it until the tree is too big to fit inside the center ring (my tree's about 1.5" now, so it has a ways to go before it won't fit in the 4" aperture).
You can get it from Amazon from Here.