I am very satisfied with this product. I have a constant problem with melting snow dripping off the metal roof of my shed that freezes again once the sun goes down. This creates a piece of solid ice that won't budge, even with a queen. Yesterday afternoon I covered part of it with a blanket. The night temperature was 15F. It completely melted this morning! Anyone who says it doesn't work has either turned it upside down or has a defective block. 5 stars so far, I hope it lasts a few years.