This heated mattress pad earned The Best rating from the Hammacher Schlemmer Institute because it generated the most consistent warmth and was the most comfortable. The Best Heated Mattress Pad's temperature fluctuated by only 0.61° F across its entire surface over eight hours, proving to be the most consistent of any model tested. Panelists who slept on the mattress pads lauded The Best model's soft cushioning and virtually undetectable heating elements. Earning a perfect score for durability, The Best model did not shrink or fray after repeated machine washing. Dual LCD controls for the king and queen sizes allow two sleepers to set their own temperature preferences from 10 heat settings and the heating elements shut off automatically after 10 hours. For mattresses up to 18" deep.