Are you talking about the big apple herp bah-500? If so I would not recommend it. It was a new product when I bought them so I called and they told me they were proportional so I ordered 5 of them. They came in the mail and they were on/off but I tested 2 of them and they dropped 5 degrees before heating again, ouch! I called them and received my money back including shipping and return shipping. There is much better on/off style thermostats out there.
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