Boston Red Sox New Era Official Onfield 59Fifty Cap - 25 City Connect - Green.  The 59FIFTY is an icon in sport and street culture thanks to its status as the official on-field cap of MLB. Embroidered graphics with raised details, Six panels with eyelets, Breathable construction, Material: 100% Polyester, Wipe clean with a damp cloth, Flat bill with ability to curve, Fitted, High Crown, Structured fit