Review on Chefman Electric Warming Tray | Adjustable Temperature Control | Ideal for Buffets, Restaurants, Parties, Events, and Home Dinners | Sleek Glass Top Surface (21” x 16”) Ensures Constant Food Warmth | Black by Divya Flood

I used my heater the day after it was delivered when we hosted a housewarming party for over 50 people. It worked exactly as I had hoped. The instructions said concrete was not thermally safe and my meters are concrete. I was worried so I tested it in my garage first and didn't see any problems. I chose to use it on my new concrete countertops and after 3 hours of running on medium there were no issues. Why don't you recommend using it on concrete? Also, there was no marking on the knob to set the temperature, so I had to make my own marking to keep it at my desired temperature. It is highly recommended to add a red mark to the handle. Otherwise the Chessman heater works well.