I bought 5 thermostatic valve that "look very good" but do not screw on the valve that is 28 mm in diameter. Amazon would do well to prevent that this article is not suitable for brand valves "SAR". So I had to buy it and I will ask 5 valves 30 mm in diameter. I have not been able to test the thermostat! It is true that in the ad, put it verbatim: mounts on almost all valves ..... BEWARE OF "ALMOST"