flexfit v cotton twill fitted 5001 thin blue line hat (small/medium (6 3/4 to 7 1/4), black) flexfit officially licensed flexfit brand 5001 cap with thin blue line patch made exclusively for go commando gear. looks and feels like wool, patch area allows you to choose what's on front. the thin blue line is a symbol of respect and support for police and law enforcement officials. show your support with the thin blue line flag cap.