MLB Oakland Athletics Black on Black 59FIFTY Fitted Cap by New Era. $24.49. 100% Wool. 59FIFTY fitted cap in fashion color. Embroidered Team logo in raised embroidery at front. Officially licensed by Major League Baseball. 59FIFTY is the official on-field cap of Major League Baseball and is worn by every Major League Baseball player. With this fashion version of the 59FIFTY you can show your team pride with style.