Best Cooling Gel Mattress Toppers King: The best ice cooling gel memory foam mattress toppers for king-size mattresses offer exceptional cooling capabilities and comfort that are especially suitable for king-size beds. To match the larger proportions of a king-size mattress, these toppers tend to come in generous sizes. This mattress topper reduces body temperature, creates a comfortable resting environment, and provides proper physical support for side sleepers and those with back discomfort, enabling them to sleep peacefully.