story: https://www.espn.com/nfl/story/_/id/40031598/nfl-allow-guardian-caps-helmets-regular-season
The NFL has adjusted its rules to allow players the option of using Guardian Caps in regular-season games to enhance their protection against head injuries, the league confirmed Friday.(http://www.autoadmit.com/thread.php?thread_id=5521766&forum_id=2#47611662)