Instruct: Classify an Amazon review as either positive or negative.
Query: The work, but they crack

I have bought over 10 of these heaters for both my house and rental properties. They do heat nicely, the only problem with them is most of them have cracked. Sometimes they crack right away, sometimes they will crack after you turn them off in the spring. I have sent many of them back and they do send you a replacement without a problem. I have even been told to use joint filler to fix the cracks. They are like square pieces of clay, with wires running through them. I think the contraction and expansion of them being turned on to heat and then cooling down when off, cracks them. I've thrown a couple of them out. Wish they would come up with a model that does not crack. Other then that they are great, they do heat.