I used to have a 130lb water bag. It was one of the water/foam variety described in that article. And it was probably one of the most useless things I've ever owned.
I'm not sure what the actual model name was, it was a Combat Sports model.
Not only was it too short to train MMA (can't punch the head and kick the legs), but it also contained a metal ring at the top of the bag (I would assume the top of the badder), that made my knuckles ache for weeks after I stopped using it, through 16oz gloves after they'd been worn down with a little use. This same metal ring got dislodged and misaligned by the accumulation of a few weeks worth of uppercuts and just one front snap that was the "straw that broke the camels back." Another issue I found with the water/foam design is that you have to penetrate 2-3 inches into the bag with each technique before connecting with a rigid surface that resists the impact.
The point I'm trying to make is that I'm not the most vigorous guy when it comes to training, not by a long shot, and I broke this bag beyond repain in less than a month. Suffice to say, I'm permanently butthurt on waterbags.
As said above me, I'd recommend a heavy bag of Thai bag. More importantly I recommend from some company that makes things specifically for MMA and Boxing, and doesn't sell their product in Wal-Mart (don't go with everlast-one of those broke pretty easily too under my abuse!). Somewhere like Title for example. A friend has a Title Thai bag and it is so amazingly well build and stiff I get a little giddy every time I hit it.
Sig courtesy of that photo-matic magician limba
I went out the way that I fight. I went out on my shield. Thatís it. Done. --Chuck Liddell
My goal is to end my opponent --Carlos Condit