Instruct: Classify Amazon reviews into positive or negative sentiment
Query: very unstatisfactory

I bought one of these for my electric stove about 1 1/2 years ago. Kind of expensive for a piece of metal at the time, but it seemed to work OK for a while until I began noticing that my pots or pans did not set flat on the plate anymore. Sure enough, the plate became noticeably warped with a hump in the middle. It was after a year of usage and I didn't pursue a replacement or refund. In the meantime I found in the bottom of my cabinet a round steel plate we must have purchased 20-30 years ago. I have been using this old one under same conditions since with excellent results - no warping.