Most pillows are filled with polyester. This one is filled with 1.5 lbs of virgin wool from Northwest U.S. farms, encased in undyed organic cotton from Texas, and handmade in northern Idaho. Wool regulates temperature naturally, doesn't flatten the way synthetic fill does, and is inherently hypoallergenic. No chemicals, no synthetics. The medium loft is the most popular, built for side and back sleepers who want real support.