I swear these used to be larger...
Seems to have an improved center connection point over the older models, which, would come apart if really having to dig in with them.  I gave my last one away to a coworker who had really bad issues with his back and when I bought this one it didn't seem to fit around the rib cage as easily as the other did.  Either way, good quality product and lets you hit anywhere tight with pin point accuracy.
Rating: 4 stars