If a player wanted to wear a Guardian Cap during a game, the league would prohibit it - NBC Sports
Guardian Caps Guardian Sports
Guardian Caps - Are the soft-shelled football helmet covers effective at limiting head injuries? - ESPN
More padding the issue of concussions and better helmets
Queen's Football utilizing Guardian Caps - Queen's University Athletics
Anything we can do to protect them: East Clarendon uses Guardian Caps to protect against concussions - The Sumter Item
NFL players don Guardian Caps, designed to protect from concussion
NFL Expands Use Of Guardian Caps In 2023 - Steelers Depot
Guardian Caps Guardian Sports
John's Journal: Park Football Team Is All In On Concussion Safety, News