The story behind those soft-shell puffy Guardian Caps players have been wearing
The Football Player's Brain That Sparked the NFL's Concussion Crisis - The Atlantic
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL hopes to reduce head injuries with helmet experiment
What are Guardian Caps? Shadow Hills football using new device to reduce head injuries
Guardian Caps Guardian Sports
NFL executive hints that Guardian Caps could eventually be worn in games, along with position-specific helmets
NFL says positions wearing Guardian Caps saw 52% decrease in concussions - NBC Sports