I will write my review again, more comprehensive this time. I initially bought the CNS 300 Trend. I was disappointed with its noise levels and decided to exchange it for the same model, hoping that I had just received a defective unit. The dealership and store were willing and helpful in replacing it for me. However, I encountered the same noise issues with the new unit. I then decided to invest in the CON 20 Premium, as it is a German product. I installed it in a well-insulated 35 square meter kitchen-living room area, protected from the north wind. With the thermostat calibrated to -0.5 degrees Celsius, the space reaches 21.5 degrees in about 45 minutes, which is where I have set the radiator's thermostat as well. It was initially quiet for the first few days, but after 4-5 days, the noise returned. The pressure rose to 21 (half a degree below room temperature). I was tired of the constant changes and had no intention of returning it, so I decided to open it up and see if I could do something about it. Upon opening it, I noticed that there were two plastic covers that had shifted from their position where the resistance connects to the various wires. I put them back in place, and the radiator became quiet again. However, after 4 days, the noise returned. I realized that these rubber pieces move on their own due to expansion and contraction, so I found a way to secure them using the screws of the wires that were already present in the radiator. Now it is completely quiet, and I am very satisfied with this product (only the thermostat makes a slight noise). They should find a way to fix this issue, which is why I am giving it 4 stars. Also, the price is overrated. I hope this helps.