Bests & Worsts Reviews from Amazon

I purchased this simmer mat to use on a glass cooktop. I placed the nipples down, next to the cooktop, as instructed. Cooked my soup and everything seemed to be great. Upon removing the mat, I noticed indentions in the cooktop left by the mat. Upon further inspection, I found that the cooktop had cracked. This $15 mat turned into a disaster. I now have to replace the cooktop.