I just recieved mine yesterday, and have my 6.5 gallon primary in there as of 4pm yesterday. I didn't plan well for being prepared with plastic bottles so I only had 3 11oz bottles on hand, and stuck those in there, and then this morning the wort was at 73 degrees. I changed out the 3 bottles with a frozen one gallon plastic jug this morning. We will see how that does.