TEIJIN - Product Name: Cool Mat & Warm Gel Pad - Size: 76 x 50cm - Materials: Surface: 100% Cotton, Middle: 100% Polyester, Back: 100% Polyester Used a few times, but stored at home for a long time. I tried heating it in a 600W microwave for 2 minutes and 10 seconds. The gel started to expand after about 1 minute and 30 seconds. I don't think there are any tears. Please purchase if you understand that this item has been stored for a long time.