Fm
As the pundit once asked, "Why is Mr. Clean coming out with a new improved version? Wouldn't you think the competition would be doing that to catch up?" Some engineer could not think of anything else to mess up, so he decided to "improve" the 400A. One thing about the Pro that I am not sure about is the "flow restrictor" in the shank, like the one in Kohler's version. It reduces the flow and the noise, but may swell up and block the flow the way Kohler's do.