I encourage everyone to buy these. They are incredibly easy to fit (20 mins for 5 radiators)and the difference they make can be felt almost immediately. We have a Victorian house with cavity walls, the freezing weather meant that even with our heating on full blast, the house was still cold. Within minutes of fitting all of them my husband turned down the heating and took off a jumper and then I turned down the heating to its lowest setting and the house was still warm - amazing.I'm sure they'll pay for themselves in a few weeks if this weather continues.