This baseball cap is made of cotton oilskin, like the McKinley. Waterproof oilskin caps in classic 6-panel construction, plain or fancied-up, have become favorites to wear before, during or after work. They are the perfect companions to all of our gear. S-21 5/8″, M-22 1/8″, L-22 1/2″ – 23″, XL-23 3/8″ – 23 3/4″ 1492