Pillowcase CoolingSIZE CHART Designed to fit all three sizes of the HEST pillow, made with HESTs jade infused cooling fabric for optimal temperature regulation, enhanced airflow and a consistently cool and comfortable fabric to lay your head during sleep in warmer conditions. "Upon the first touch, you can immediately feel the cooling fabric take effect! For someone who sleeps on the warmer side, having a cooling fabric to lay my head on is amazing.. Calvin Y., HEST