Look no further than the NBA Store for iconic headwear from the best brands in sports. Browse our selection of Boston Celtics flex hats to find the design that best fits your gameday look. Find the hottest NBA flex hats for friends and family as a great gift. Every fan will love showing off a Celtics flex hat at the arena. The NBA Store only offers Celtics flex caps that are officially licensed by the NBA, so you can be sure you're sporting an authentic style.