When you want to control something the first question that comes to mind is how well do you want to control it? So, there is no spec and so I offered the newest and greatest in research, as noted on the very first response, "Just for Reference...". MFA and other close representatives are quite well known as the lazy man's controller. Of course everyone wants more control over what they're controlling, but how much do you really need? That makes the controller. Previously in the thread, "... is looking for water kept REALLY constant. The best I have seen is 0.05 degree C if you can do better google and contact. " Only a better controller can handle this.