I just used one for a new installation and love it. Nicely made (all metal; the faceplate in the similar Hangrohe unit is chrome-plated plastic), and the central large lever or knob keeps the consistant temperature you set it at. It's actually labelled in elegant imbossed degrees F, so you can set and forget it once you find your fave temp. The lower and upper smaller knobs turn 90 degrees to the side and are volume controls for two outlets - usually the tub spout for the lower control and the showerhead for the upper. However it could also be two showerheads or something else. The two outlets can be turned on or off seperately or together. My tub spout will have a diverter for a handshower, so it can be used at the same time as the wallmount showerhead, with adjustable water volume between the two.. High rate of water flow compared to some other brands. Highly recommended.
Here is a link that might be useful: California Faucets rectangular Thermostatic Trims
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cali faucet tub shower handshower setup
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