NBA Men's Boston Celtics HWC Kalvin Snapback Cap (Black, OSFA) by '47 Brand. $27.99. 85% Wool, 15% Acrylic. Crisp, fresh stitching. 47 Brand provides the quality all true fans desire in their gear. Known for their vintage look and feel, '47 has managed to also provide a new school spin to this old school craze. Featuring tight, crisp stiching; 47 Brand has made their claim as the source for snapbacks. Snap this hat and never look back.