Copper is a metal that does not disperse heat evenly. Usually the center could have a lot more heat than the outsides and this type of uneven high heat could cause your pot to crack. So avoid using a cooper diffuser with your MEC pure-clay pots and pans. Diffusers made of cast iron, carbon steel or aluminum should work fine. If using on glass/ceramic cook tops, we recommend this ventilated diffuser as opposed to a non-ventilated one.