I don’t know how but it was cool as soon as I took it out of the package. I didn’t even need to place it in the freezer and it was cold already and stayed cold for hours.I am not sure but I have a hard time getting my cat to lay on this. She is a long haired cat, though. So she prefers to lay on the deep freezer.Was disappointed that this pad does not have more cushioning, as it is made of very thin material. When my pet got on the pad, it was like he was trying to lay on a flat piece of material and not a comfortable cooling pad. After testing it out, my pet will not go back on it.It is solid color with no designs (unlike the pictures of the item, which are misleading).I feel the pad is not worth the price that was paid for it and definitely would not recommend this pad.Wish it were larger. My dog is 130 lbsLike a quilted baby blanket. Curled up and moved when dogs got on it. XL was like large.I was expecting a real cooling mat. This was fabric with openings on the back for air to go through. It’s still nice and my cats lay on it but it wasn’t what I expected.I bought two of these for my dogs and they will use them when they are placed on their beds but not sure they really are cooler than the bed itself.I hadn’t heard about cooling mats for pets, but as soon as I did, I knew it was something my cat needed, as my apartment lacks a central A/C system. I decided on this one because the price was good. I’ve had it for about a week now, and my cat seems to have adopted it as his new preferred napping spot. I couldn’t effectively tell you if it does its job of keeping him cool, but I’m led to believe it does since he now prefers it to the hardwood floor. A great purchase!