Guardian Cap: What are and why the NFL asks this safety measure in helmets
Guardian Cap debuts during minicamps in effort to reduce avoidable head contact
Guardian Caps: What are they and why are NFL players wearing them? - Sactown Sports
What is the Q Collar, the device NFL players are wearing around their necks
NFL CMO Dr. Allen Sills explains importance of mandated guardian caps during training camp
NFL hopes to reduce head injuries with helmet experiment
Guardian Caps, a soft-shell helmet cover, among CFL's new player-safety initiatives
Guardian Caps: Why some NFL players are wearing them in training camps
EXPLAINER: NFL using helmet caps for player safety, research - The San Diego Union-Tribune
With a little imagination NFL's new Guardian Caps take on different look in Cleveland: Crowquill
John's Journal: Park Football Team Is All In On Concussion Safety, News