I was really excited about this heating mat because it鈥檚 cold in my room and I wanted to heat my resin while in the mould to reduce bubbles. I have expensive moulds and they were on the heating mat no more than an hour and the coaster holder mould warped and now it鈥檚 unusable. Be careful when using it that you don鈥檛 leave your moulds on high for too long. I believe the instructions say you can keep them on for 4 hours. It depends on the mould. I won鈥檛 use it anymore because I don鈥檛 want to risk ruining another $100 mould.